Weight Management Interventions Provided by a Dietitian for Adults with Overweight or Obesity: An Evidence Analysis Center Systematic Review and Meta-Analysis

Abstract

Background

Obesity is associated with a multitude of comorbidities and considerable health care costs.

Objective

The objective of this review was to examine the efficacy of weight management interventions provided by a registered dietitian or international equivalent (referred to as “dietitian”).

Methods

This systematic review and meta-analysis of randomized controlled trials (RCTs) examined the effect of weight management interventions provided by a dietitian, compared with usual care or no intervention, on several cardiometabolic outcomes and quality of life in adults with overweight or obesity. MEDLINE, Embase, PsycINFO, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, and CINAHL databases were searched for eligible RCTs published between January 2008 and January 2021 in the English language. Meta-analyses were conducted using a random-effects model, publication bias was assessed using funnel plots and Egger’s statistics, and heterogeneity was assessed by interpreting I² values. Efficacy of intervention components, such as telehealth or group contacts, were explored in sub-group analyses. Version 2 of the risk-of-bias tool for RCTs was used to assess risk of bias. The Grading of Recommendations Assessment, Development and Evaluation method was used to determine certainty of evidence.

Results

This systematic review included 62 RCTs. Compared with control conditions, weight management interventions provided by a dietitian resulted in improved body mass index (mean difference [MD] −1.5; 95% CI −1.74 to −1.26; moderate evidence certainty); percent weight loss (MD −4.01%; 95% CI −5.26% to −2.75%; high evidence certainty); waist circumference (MD −3.45 cm; 95% CI −4.39 to −2.51 cm; high evidence certainty); blood pressure (MD −3.04 mm Hg; 95% CI −5.10 to −0.98 mm Hg and MD −1.99 mm Hg; 95% CI −3.02 to −0.96 mm Hg for systolic blood pressure and diastolic blood pressure, respectively; moderate and low evidence certainty); and quality of life using the 36-Item Short Form Survey (MD 5.84; 95% CI 2.27 to 9.41 and 2.39; 95% CI 1.55 to 3.23 for physical and mental quality of life, respectively; low and moderate evidence certainty).

Conclusions

For adults with overweight or obesity, weight management interventions provided by a dietitian are efficacious for improving several examined cardiometabolic outcomes and quality of life.

More than 39% of the adult population world-wide is classified as having overweight or obesity based on body mass index (BMI; calculated as kg/m²).¹ Obesity is associated with a variety of comorbidities, including cardiovascular disease, type 2 diabetes mellitus (T2DM), and certain forms of cancer.^2–4 In addition, obesity is associated with mental health conditions and lower quality of life (QoL).^5,6 Obesity-related comorbidities are economically costly. For example, annual costs are estimated to be $190.2 billion, or more than 20% of medical spending in the United States alone.⁷ Up to $425 billion per year (US dollars) is spent treating diseases caused by overweight across countries that are members of the Organisation for Economic Co-operation and Development, G20, and European Union.⁸

Registered dietitians, registered dietitian nutritionists, or international equivalents (referred to as “dietitians” hereafter) are key interventionists in providing education, motivation, and techniques to treat overweight and obesity. A prior systematic review demonstrated the efficacy of dietitians providing weight management interventions for adults in the primary care setting.⁹ However, the systematic review was limited to interventions delivered on an individual level in a specific setting, and adults were not required to have overweight or obesity. More information is needed regarding the effect of dietitians working in a variety of settings (eg, workplace or community), with a variety of populations (eg, adults with T2DM and older adults), and using a variety of methods (eg, group-based or telehealth interventions). Although some of these factors were addressed in a 2014 evidence-based guideline on adult weight management from the Academy of Nutrition and Dietetics (Academy),¹⁰ much of the evidence supporting the guideline was from a 2008 systematic review, and recommendations guiding specific intervention methods were not supported by a systematic review. Dietetics practice and research have evolved and require re-examination of current literature to guide contemporary practice.

Dietitians play a pivotal role in treating overweight and obesity and have the potential to facilitate considerable reductions in health care costs associated with overweight and obesity comorbidities and treatment. It is essential to address the current gaps in knowledge to inform evidence-based overweight and obesity treatment. Thus, the aim of this systematic review was to examine current evidence on adult weight management interventions provided by a dietitian to support an updated version the 2014 evidence-based guideline described above.¹⁰ The following research question was addressed in this systematic review: In adults with overweight or obesity, what is the effect of weight management interventions provided by a dietitian, compared with usual care or no intervention from a dietitian, on BMI, percent weight loss, waist circumference (WC), blood pressure (BP), fasting blood glucose (FBG), QoL, cost-effectiveness, and adverse events?

METHODS

Study Design

This systematic review adheres to protocols from the Academy’s Evidence Analysis Center (EAC),¹¹ as well as the Cochrane Collaboration’s GRADE (Grades of Recommendation, Assessment, Development and Evaluation) method,¹² and reports Preferred Reporting Items for Systematic Reviews and Meta-Analyses.¹³ The research questions, eligibility criteria, and methods were registered a priori at PROSPERO (CRD42021230850).¹⁴ An expert panel of dietitians was recruited and selected by the Academy’s Council on Research Work Group Selection Subcommittee and, in collaboration with systematic review methodologists, formulated the research question, participated in the systematic review process, and advised on overweight and obesity treatment-related content.

Eligibility Criteria

Details of eligibility criteria can be found in Figure 1. To be included, primary studies were required to examine adults with overweight or obesity (BMI ≥25 or as defined by the study authors for a specific population). The intervention of interest was weight management counseling/education provided by a dietitian, although the intervention may have also included treatment from other professionals, such as physicians, exercise physiologists, and/or psychologists. The comparison group was required to be usual care or no intervention. Outcomes of interest were selected and prioritized by the expert panel based on importance to health and applicability to practice, and included BMI, percent weight loss, WC, BP, FBG, QoL, and cost-effectiveness. Adverse events were also included as outcomes of interest. The expert panel’s initial intention was to analyze percent weight loss as a continuous variable. However, many studies only reported percent weight loss as a proportion of participants achieving 5% weight loss. Therefore, both outcome measures were accepted and included in separate meta-analyses.

Figure 1.

Eligibility criteria for the systematic review examining the effect of adult weight management interventions provided by a dietitian for adults with overweight or obesity.

A priori, the systematic review team specified that if randomized controlled trials (RCTs) were available for an outcome of interest, these would be prioritized over nonrandomized trials. Articles were restricted to those published in the English language due to resource constraints. A beginning cutoff date of 2008 was selected to assess evidence published since the previous systematic review search ended in 2008, and because an earlier scoping review identified considerable relevant research published since 2008.¹⁵

Information Sources and Search Strategy

An information specialist searched the literature for peer-reviewed articles published in the English language between January 1, 2008 and January 25, 2021. MEDLINE, Embase, PsycINFO, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, and CINAHL databases were searched to identify controlled trials and systematic reviews focusing on weight loss or weight management interventions for adults. The search combined terms for overweight or obesity and lifestyle, behavioral, or diet interventions. Relevant systematic reviews were hand searched for applicable articles not identified in the databases search. The full search strategy can be found in Figure 2 (available at www.jandonline.org).

Figure 2.

Full search strategy for systematic review examining the effect of adult weight management provided by a dietitian for adults with overweight or obesity.

Selection Process

Each title/abstract identified by the databases search was reviewed by 2 independent EAC reviewers using Rayyan databases screening software.¹⁶ Any discrepancies between these reviewers were settled by consensus. For any remaining conflicts, the title/abstract moved on to the next phase of full-text screening.

After removing conference abstracts and studies with the wrong study design, full texts of potentially included articles were reviewed by 2 independent reviewers. One review was conducted by an EAC methodologist and a second review was conducted by an expert panel member. Any discrepancies were settled by team consensus or by a third review. If more information was needed to determine inclusion (eg, if it was not clear whether the interventionist was a dietitian), the corresponding author of the article was contacted for clarification.

Data Items and Extraction

Data extraction was conducted by trained evidence analysts using an online, customized, data extraction tool. Data extracted included study design and bibliographic information, funding source, dropout rate, and participant characteristics (eg, sex, age, and race and ethnicity). In addition, evidence analysts extracted all study information needed to answer sub-questions and identify sub-populations and outcomes of interest specified a priori (see Synthesis of Results section). All data extracted were reviewed by EAC staff. Quantitative results extracted for continuous variables included mean change, variance, and sample size for each group. If mean change was not available for each group, but study authors reported pre and post values, mean change was calculated using Open MetaAnalyst.¹⁷ For the outcome of 5% weight loss, incidence was reported as number of events (individuals achieving 5% weight loss) per sample size. Quantitative results were extracted directly from the article into a standardized Excel spreadsheet and all results were reviewed by the expert panel. If a study was missing information of interest, the study’s corresponding author was contacted to request these data. Follow-up data after the interventions are not reported in this review, but can be found in full on the Evidence Analysis Library website.¹⁸

Risk-of-Bias Assessment

RCTs were assessed for risk of bias (study quality) using version 2 of the risk-of-bias tool for assessing risk of bias in randomized trials.¹⁹ This tool included assessment of potential bias from the randomization process, deviations from the intended intervention, missing outcomes data, measurement of outcome, and selection of the reported result. EAC staff and trained evidence analysts conducted 2 independent assessments and any discrepancies were settled by consensus or a third review. Final study ratings were classified as low risk of bias, some concerns, or high risk of bias.

Effect Measures

For outcomes measured as continuous variables, the effect measures reported in the meta-analysis were mean difference (MD) and 95% CI between groups. For categorical variables, the effect measures in meta-analysis were risk ratio and 95% CI of events in the intervention groups compared with the control groups.

Certainty Assessment

Certainty of evidence was determined using the GRADE method¹² and reported as a summary of findings table. Certainty of evidence was graded as “high,” “moderate,” “low,” or “very low,” depending on study designs, collective risk of bias, inconsistency in findings, indirectness, imprecision, and other factors.²⁰

Synthesis of Results

When outcome measures were similar enough to be meaningfully combined, meta-analyses were conducted for each outcome of interest using a random-effects model and the DerSimonian-Laird method with inverse-variance weighting. OpenMeta Analyst¹⁷ and RStudio²¹ software programs were used for meta-analyses and generation of forest and funnel plots. If study authors did not provide sample size and mean change and variance (or pre and post values) for each group, studies were included in the narrative write-up only. Heterogeneity was reported using I² values. CIs for I² values were constructed using the DerSimonian-Laird or Paule-Mandel methods. Publication bias was reported using funnel plots and assessed using the Egger’s statistic for outcomes reported by ≥10 included studies.²² Authors conducted sensitivity analyses using leave-one-out analysis and by comparing effect sizes according to study quality. Study characteristics and intervention components, as well as summary of findings, were reported in tables.

Impact of intervention components were explored using sub-group analyses for components determined a priori by the expert panel, including interventions delivered via telehealth or in-person or hybrid; interventions delivered individually or in groups or hybrid; interventions delivered by a dietitian alone or multidisciplinary interventions; number and frequency of contacts with the dietitian; and duration of the intervention. Although the authors recognize that comparing effect sizes from subgroup analyses does not imply that the differences are statistically or clinically significant, examining patterns in data according to effect sizes compared with controls may explain some heterogeneity in results and inform practitioners. The summary of findings table was adapted from the summary of findings and evidence profile tables from GRA- DEpro.²³ The risk-of-bias figure was based on the robvis tool.²⁴

RESULTS

Literature Search and Study Characteristics

The databases search identified 19,464 titles/abstracts. The full-texts of 936 articles were reviewed and a total of 73 articles,^25–97 representing 62 RCTs, were included in this systematic review. All outcomes of interest were reported in RCTs; non-RCTs were not included. The study inclusion process is described in Figure 3.¹³ Study characteristics and intervention components are described in Table 1 and Table 2, respectively. As shown in Table 1, 24 RCTs were conducted in the United States ^{25,28,29,33,34,38–42,54,56,67,69,71,77,80,82, 84,88,89,93,94,97} and 38 RCTs were conducted in other countries.^{26,27,30–32,35–37,43,44,46,47,49,51–53,55,58–62,65,66,68,70,74–76, 78,79,81,83,86,87,90,92,96} Intervention settings were outpatient (n = 31 RCTs) ^{26,27,30,31,33–36,43,44,47,49,51–53,55,58,61, 65,66,69–71,74,76,78–80,89,93,96} community (n = 8 RCTs) ^{28,29,37,54,56,59,75,86} _workplace (n = 5 RCTs) ^{39,68,82,83,97} research/university (n = 11 RCTs) ^{32,38,40,42,46,62,81,88,90,92} and not reported/other (n = 7 RCTs).^{25,60,67,77,84,87,94} Dietary advice was described in all but 16 Studies ^{25,32,33,52,54,58,60,65,71,75,76,79,81,83, 84,87} Of the 46 studies that did report dietary advice, 38 studies reported that caloric restriction was advised ^{26–31,35,42,44,46,47,49,53,55,56,59,61,62,66,68,70,74,77,78,80, 82,88,89,92–94,96} as Table 2 shows, interventions were provided by a dietitian alone in 31 RCTs ^{26,27,30–32,34,39,40,42, 43,46,47,52–56,59,61,68–70,78,80,82,84,87,89,92,93,97} and by a multidisciplinary team that included a dietitian in 31 RCTs.^{25,28, 29,33,35–38,41,44,49,51,58,60,62,65–67,71,74–77,79,81 83,86,88,90,94,96}

Figure 3.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart¹³ describing inclusion process for systematic review examining the effect of adult weight management interventions provided by a dietitian for adults with overweight or obesity. RCT = randomized controlled trial.

Table 1.

Characteristics of studies included in the systematic review examining the effect of adult weight management interventions provided by a dietitian for adults with overweight or obesity

Study first author, year	Country	Target population or comorbidity	Age (mean ± SDa or range), sex	Sample size, n	Duration, mo	Follow-up duration, mo	Setting	Funding source	Risk of bias18
Abd El-Kader, 201647	Saudi Arabia	Adults with obesity	47–58 y, Fb	80	3	0	Outpatient	University	Some concerns
Abd El-Kader, 202048 Abd El-Kader, 201849	Saudi Arabia	Adults with obesity and type 2 diabetes	35–55 y, Mc and F	80	3	0	Outpatient	University	High
Alencar, 201925	United States	Adults with obesity	23–64 y, M and F	25	3	0	NRd	Government	Some concerns
Al-Hamdan, 201926	Saudi Arabia	Adults with overweight and prediabetes	18–55 y, F	123	3	3	Outpatient	University	High
Almanza-Aguiler, 201827	Spain	Adults with obesity	35–55 y, F	57	12	0	Outpatient	Government	High risk
Annesi, 200828	United States	Adults with obesity	21–65 y	192	6	0	Community	Industry/not- for-profit	Some concerns
Anton, 201129	United States	Adults with overweight who were sedentary and had mild to moderate functional limitations	55–79 y, F	32	6	0	Community	Government/ not-for-profit	Some concerns
Assunção, 201030	Brazil	Adults with overweight or obesity	20 y or older, M and F	192	6	0	Outpatient	Government	Some concerns
Barratt, 200831	United Kingdom	Adults with type 2 diabetes	18–75 y, M and F	50	6	0	Outpatient	NR	Some concerns
Beleigoli, 202032	Brazil	Adults with overweight or obesity	18–60 y, M and F	473	6	0	Research/ university	Government	High
Bennett, 201034	United States	Adults with obesity and hypertension	25–65 y, M and F	85	3	0	Outpatient	Government University/ hospital	Low
Bennett, 201833	United States	Adults with obesity, hypertension, diabetes, hyperlipidemia	21–65 y, M and F	337	12	0	Outpatient	Government	Some concerns
Bertz, 201235	Sweden	Adults who were postpartum with prepregnancy overweight or obesity	33.3 y, F	31	3	9	Outpatient	Government	Low
Bove, 202036	Denmark	Adults with overweight and cardiovascular disease	40–75 y, F	56	6	0	Outpatient	University/ hospital Not-for-profit	Low
Cai, 201937	China	Older adults with obesity	60 y or older, M and F	422	24	0	Community	Government	Some concerns
Carnie, 201339	United States	Adults with overweight	46 ± 10.5 y, F	139	6	0	Workplace	Government	Some concerns
Chambliss, 201140	United States	Adults with overweight	45 ± 10.3 y, M and F	62	3	0	Research/ university	Industry	Some concerns
Colleran, 201242	United States	Adults who were postpartum with overweight	23–37 y, F	27	4	0	Research/ university	Government University	Some concerns
de Freitas, 202043	Brazil	Adults with obesity	20 y or older, F	57	6	0	Outpatient	Government University	Low
de Vos, 201444	Netherlands	Adults with overweight	50–60 y, F	366	30	0	Outpatient	Government	Some concerns
Duncan, 202046	Australia	Adults with overweight or obesity	19–65 y, M and F	54	12	0	Research/university	Government	Low
Gallagher, 201251	Australia	Adults with overweight or obesity, heart disease and type 2 diabetes	18–80 y,	133	4	0	Outpatient	University	Some concerns
Gandler, 201652	Australia	Adults with obesity	<75 y, M and F	36	12	0	Outpatient	Hospital	Some concerns
Georgoulis, 202053	Greece	Adults with overweight or obesity and moderate or severe obstructive sleep apnea	18–65 y, M and F	85	6	0	Outpatient	University	Some concerns
Gilmore, 201754	United States	Adults who were postpartum and low income	18 y or older, F	35	4	0	Community	Government	Some concerns
Hageman, 201756	United States	Adults who were overweight or obese	40–69 y, F	149	18	12	Community	Government University Hospital	Low
Hardcastle, 201357 Hardcastle, 200858	United Kingdom	Adults who were overweight or obese or had hypertension or hyperlipidemia	18–65 y, M and F	67	6	12	Outpatient	Not-for-profit	High
Hassapidou, 202059	Greece	Adults with overweight or obesity	54.1 ± 14.9 y, M and F	4026	6	0	Community	Government	High
Haste, 201760	England	Adults with obesity and type 2 diabetes	18 y or older, M	32	12	0	NR	Government	Some concerns
Hollis, 202061	Australia	Adults with obesity	18 y or older, M and F	46	2	0	Outpatient	Government	Low
Hurkmans, 201862	Belgium	Adults with overweight or obesity	18–65 y, M and F	36	3	0	Research/ university	Industry	High
Innes, 201965	United Kingdom	Adults with obesity	18–50 y, M and F	42	3	0	Outpatient	Not-for-profit	Some concerns
Jiang, 201766	China	Adults with obesity and type 2 diabetes	18–70 y, M and F	119	12	0	Outpatient	NR	Some concerns
Johnson, 201967	United States	Adults with obesity	43.3 ± 11.2 y, M and F	20	3	0	NR	Government	High
Karintrakul, 201768	Thailand	Adults with overweight or obesity	19–60 y, F	41	3	0	Workplace	University	Some concerns
Kesman, 201169	United States	Adults with obesity	18–75 y, M and F	44	6	6	Outpatient	Hospital	Some concerns
LEVAe in Real Life trial: Hagberg, 201955 Huseinovic, 201663 Huseinovic, 201864	Sweden	Adults who were postpartum with overweight or obesity	32.2 ± 4.6 y, F	87	12	12	Outpatient	Government	Low
Liljensøe, 202170	Denmark	Adults with obesity and osteoarthritis	46–85 y, M and F	66	14	0	Outpatient	Industry Not-for-profit	Some concerns
LITOEf trial: Colleluori, 201941 Villareal, 201795	United States	Adults who were older with or obesity	65 y or older, M and F	71	6	0	Research	Government	Some concerns
Ma, 201371	United States	Adults with overweight or obesity and prediabetes	18 y or older, M and F	146	15	0	Outpatient	Government Not-for-profit	Low
Muggia, 201474	Italy	Adults with overweight or obesity	18–65 y, M and F	78	6	6	Outpatient	NR	Low
NEWg trial: Campbell, 201238 Duggan, 202145 Foster-Schubert, 201250 Mason, 201172 Mason, 201973	United States	Adults who were postmenopausal with overweight or obesity	50–75 y, F	196	12	0	Research	Government	Low
Nilsen, 201176	Norway	Adults with overweight or obesity at risk of type 2 diabetes	18–64 y, M and F	182	18	0	Outpatient	Not-for-profit	Low
O’Neil, 201677	United States	Adults with overweight or obesity and type 2 diabetes	18–70 y, M and F	460	12	0	Other	Industry	Some concerns
Pablos, 201778	Italy	Adults with overweight or obesity who were low- income	20–70 y, M and F	68	8	0	Outpatient	NR	Low
Padwal, 201779	Canada	Adults with obesity	18 y or older, M and F	297	3	3	Outpatient	Government	High
Parker, 201480	United States	Adults with overweight or obesity	18 y or older, M and F	76	3	0	Outpatient	Not-for-profit	Some concerns
Rollo, 202081	Australia	Adults who were postpartum with overweight or obesity	18–45 y, F	23	6	0	Research	Not-for-profit	High
Salinardi, 201382	United States	Adults with overweight or obesity	21 y or older, M and F	118	6	0	Workplace	Government	Some concerns
SCOPh trial: Nakade, 201275 Tanaka, 201985	Japan	Adults with overweight or obesity	40–64 y, M and F	207	12	0	Community	Government	Some concerns
Shrivastava, 201783	India	Adults with overweight or obesity	25–55 y, M and F	267	6	0	Workplace	Industry	Some concerns
Svetkey, 201584	United States	Adults with overweight or obesity	18–35 y, M and F	209	24	0	NR	Government	Some concerns
Tapsell, 201786	Australia	Adults with overweight or obesity	25–54 y, M and F	106	12	0	Community	Industry Not-for-profit	High
Teeriniemi, 201887	Finland	Adults with overweight or obesity	20–60 y, M and F	121	12	12	NR	Government Not-for-profit	High
Thomas, 201988	United States	Adults with overweight or obesity	18–70 y, M and F	125	18	0	Research/university	Government	High
Trepanowski, 201789	United States	Adults with overweight or obesity	18–65 y, M and F	48	12	0	Outpatient	Government	Low
Uemura, 201990	Japan	Adults with overweight or obesity	40 y or older, F	44	2	0	Research/ university	University	Some concerns
van Gemert, 201591 van Gemert, 201592	Netherlands	Adults with overweight or obesity	50–69 y, F	139	2.5	0	Research/ university	Not-for-profit	Some concerns
Ventura Marra, 201993	United States	Adults with obesity and hypertension, hyperlipidemia, prediabetes or diabetes	40–70 y, M	56	3	0	Outpatient	Government Not-for-profit	Some concerns
Villareal, 201194	United States	Adults who were older with obesity	65 y or older, M and F	48	12	0	NR	Government Not-for-profit	Some concerns
Vissers, 201096	Belgium	Adults with overweight or obesity	44.8 ± 12.2 y, M and F	36	12	0	Outpatient	University	Some concerns
Weinhold, 201597	United States	Adults with overweight or obesity	18–65 y, M and F	68	4	3	Workplace	Government	Low

^aSD = standard deviation.

^bF = female.

^cM = male.

^dNR = not reported.

^eLEVA = Lifestyle for Effective Weight Loss During Lactation.

^fLITOE = Lifestyle Intervention Trial in Obese Elderly.

^gNEW = Nutrition and Exercise in Women.

^hSCOP = Saku Control Obesity Program.

Table 2.

Intervention characteristic of studies included in a systematic review on the effect of weight management interventions provided by a dietitian for adults with overweight or obesity

Study first author, year	Intervention duration, mo	No. of contacts	Frequency of sessions	In person, remote, or blended	Group, individual, or blended	Include PAa?	Self-monitoring?	Behavior-modifying therapy?	Professionals involved	Diet (caloric restriction, macronutrient change, dietary patternb)	Outcomes reported
Abd El-Kader, 201647	3	1	0.33/mo	In person	NRc	Yes	No	No	Dietitian	Caloric restriction	BMId
Abd El-Kader, 202048 Abd El-Kader, 201849	3	1	0.3/mo	In person	Individual	Yes	No	No	Dietitian Physical therapist	Caloric restriction	BMI
Alencar, 201925	3	14	4/mo	Remote	Individual	Yes (Ee)	Yes	Yes	Dietitian Physician	NR	% weight loss BPf
Al-Hamdan, 201926	3	6	2/mo	In person	Individual	Yes (E)	No	No	Dietitian	Caloric restriction Modified macronutrient	BMI % weight loss WCg FBGh BP
Almanza-Aguiler, 201827	12	13	1.08/mo	In person	Individual	Yes (E)	No	No	Dietitian	Caloric restriction Modified macronutrient Dietary pattern	BMI WC FBG BP
Annesi, 200828	6	6	1/mo	In person	Group	Yes	No	Yes	Dietitian Exercise/ fitness specialist	Caloric restriction Dietary pattern	BMI WC BP
Anton, 201129	6	24	6/mo	In person	Group	Yes	Yes	Yes	Dietitian Exercise physiologist	Caloric restriction Modified macronutrient	Adverse events
Assunção, 201030	6	6	1/mo	In person	Individual	Yes (E)	No	Yes	Dietitian	Caloric restriction Dietary pattern	BMI % weight loss WC FBG BP
Barratt, 200831	6	6	1/mo	In person	Individual	Yes (E)	Yes	Yes	Dietitian	Caloric restriction	BMI % weight loss WC BP
Beleigoli, 202032	6	12	2/mo	Remote	Individual	Yes (E)	Yes	Yes	Dietitian	NR	BMI % weight loss
Bennett, 201034	3	4	1.33/mo	Blended	Individual	Yes (E)	Yes	Yes	Dietitian	Dietary pattern	BMI % weight loss WC BP
Bennett, 201833	12	18	1.5/mo	Remote	Individual	Yes (E)	Yes	Yes	Dietitian Physician	NR	BMI % weight loss WC FBG BP Adverse events
Bertz, 201235	3	2	1/mo	In person	Individual	Yes	Yes	Yes	Dietitian Physical Therapist	Caloric restriction Modified macronutrient Dietary pattern	BMI
Bove, 202036	6	11	1.8/mo	In person	Blended	Yes	No	No	Dietitian Physical Therapist	Caloric restriction Modified macronutrient Dietary pattern	WC BP
Cai, 201937	24	36	1.5/mo	In person	Blended	Yes	Yes	Yes	Dietitian Community Clinicians	Caloric restriction	% weight loss Dietary pattern WC FBG BP
Carnie, 201339	6	16	2.67/mo	In person	Blended	Yes (E)	Yes	Yes	Dietitian	Caloric restriction	% weight loss WC
Chambliss, 201140	3	21	7/mo	Blended	Blended	Yes (E)	Yes	Yes	Dietitian	Caloric restriction Dietary pattern	BMI % weight loss WC BP
Colleran, 201242	4	16	4/mo	In person	Individual	Yes	Yes	No	Dietitian	Caloric restriction Dietary pattern	BMI % weight loss
de Freitas, 202043	6	12	2/mo	In person	Blended	Yes (E)	No	Yes	Dietitian	Modified macronutrient Dietary pattern	BMI WC FBG
de Vos, 201444	30	4	0.13/mo	In person	Individual	Yes	No	Yes	Dietitian Physical therapist	Caloric restriction Modified macronutrient	QoLi BMI % weight loss
Duncan, 202046	12	1	0.08/mo	In person	Individual	Yes (E)	No	Yes	Dietitian	Caloric restriction Dietary pattern	WC
Gallagher, 201251	4	4	1/mo	In person	Blended	Yes	Yes	Yes	Dietitian Exercise Physiologist Nurse Psychologist	Modified macronutrient Dietary pattern	BMI % weight loss WC BP
Gandler, 201652	12	5	0.42/mo	Blended	Individual	No	No	Yes	Dietitian	NR	BMI % weight loss
Georgoulis, 202053	6	7	1.16/mo	In person	Group	Yes (E)	Yes	Yes	Dietitian	Caloric restriction Dietary pattern	BMI % weight loss WC FBG BP
Gilmore, 201754	4	16	4/mo	Remote	Individual	Yes	No	Yes	Dietitian	NR	WC BP
Hageman, 201756	18	52	2.9/mo	Remote	Individual	Yes (E)	Yes	No	Dietitian	Caloric restriction Dietary pattern	% weight loss WC FBG BP
Hardcastle, 201357 Hardcastle, 200858	6	2	0.33/mo	In person	Individual	Yes	No	Yes	Dietitian Physical activity specialist	NR	BMI BP
Hassapidou, 202059	6	13	2.2/mo	In person	Individual	Yes (E)	No	No	Dietitian	Caloric restriction Modified macronutrient Dietary pattern	BMI % weight loss WC
Haste, 201760	12	21	1.75/mo	Blended	Individual	Yes (E)	Yes	Yes	Dietitian Exercise experts	NR	BMI % weight loss WC
Hollis, 202061	2	5	2.5/mo	In person	Individual	No	No	No	Dietitian	Caloric restriction	QoL WC
Hurkmans, 201862	3	1	0.33/mo	In person	Individual	Yes (E)	Yes	Yes	Dietitian Physical activity coach	Caloric restriction	BMI
Innes, 201965	3	12	4/mo	In person	Blended	Yes	No	Yes	Dietitian Exercise professional	NR	BMI % weight loss WC FBG BP
Jiang, 201766	12	1	0.08/mo	In person	Blended	Yes	Yes	Yes	Dietitian Physician Psychologist	Caloric restriction	BMI % weight loss FBG
Johnson, 201967	3	12	4/mo	In person	Blended	Yes (E)	Yes	No	Dietitian Exercise Physiologist Physician	Dietary pattern	BMI % weight loss FBG
Karintrakul, 201768	3	6	2/mo	Blended	Individual	Yes (E)	Yes	Yes	Dietitian	Caloric restriction	BMI % weight loss WC
Kesman, 201169	6	4	0.67/mo	Blended	Individual	No	No	Yes	Dietitian	Dietary pattern	% weight loss
LEVAj in Real Life trial: Hagberg, 201955 Huseinovic, 201663 Huseinovic, 201864	12	16	1.33/mo	Blended	Individual	Yes (E)	Yes	Yes	Dietitian	Caloric restriction Modified macronutrient Dietary pattern	BMI % weight loss WC QoL Cost effectiveness
Liljensøe, 202170	14	16	1.14/mo	In person	Group	No	No	Yes	Dietitian	Caloric restriction	QoL BMI BP Adverse events
LITOEkg trial: Colleluori, 202041 Villareal, 201795	6	26	4.3/mo	In person	Individual	Yes	No	Yes	Dietitian Exercise trainers	Caloric restriction	QoL % weight loss Adverse events
Ma, 201371	15	24	1.6/mo	Blended	Blended	Yes	Yes	Yes	Dietitian Fitness instructor	NR	BMI % weight loss WC FBG BP Adverse events
Muggia, 201474	6	2	0.33/mo	In person	Group	No	No	Yes	Dietitian Physician Psychologist	Caloric restriction Dietary pattern	% weight loss
Newl Trial: Campbell, 201238 Duggan, 202045 Foster-Schubert, 201250 Mason, 201172 Mason, 201973	12	27	2.25/mo	In person	Blended	Yes	Yes	Yes	Dietitian Exercise professional	Caloric restriction Modified macronutrient	BMI % weight loss WC FBG Adverse events
Nilsen, 201176	18	8	0.4/mo	In person	Blended	Yes (E)	No	Yes	Dietitian Physiotherapist Physician Nurse Ergonomist	NR	BMI WC FBG BP
O’Neil, 201677	12	2	0.167/mo	Blended	Blended	Y(E)	Yes	No	Dietitian Program staff	Caloric restriction Modified macronutrient Dietary pattern	% weight loss WC FBG BP Adverse events
Pablos, 201778	8	16	2/mo	NR	Blended	Yes	No	Yes	Dietitian Exercise trainers Psychologists	Caloric restriction Modified macronutrient Dietary pattern	BMI WC FBG
Padwal, 201779	3	13	4.33/mo	In person	Group	No	No	No	Dietitian Exercise physiologist Nurse Psychologist	NR	QoL BMI % weight loss BP Cost-effectiveness
Parker, 201480	3	4	1.33/mo	NR	Individual	Yes	Yes	Yes	Dietitian	Caloric restriction Modified macronutrient Dietary pattern	FBG
Rollo, 202081	6	6	1/mo	Remote	Individual	Yes (E)	Yes	Yes	Dietitian Exercise Physiologist	NR	BMI % weight loss WC FBG BP
Salinardi, 201382	6	18	3/mo	In person	Group	No	No	Yes	Dietitian	Caloric restriction Modified macronutrient Dietary pattern	BMI FBG BP
SCOPm trial: Nakade, 201275 Tanaka, 201985	12	11	0.9/mo	Blended	Individual	Yes	Yes	Yes	Dietitian Exercise instructor	NR	BMI % weight loss WC
Shrivastava, 201783	6	12	2/mo	In person	Group	Yes (E)	No	No	Dietitian Physical trainer Physician	NR	BMI % weight loss WC FBG BP
Svetkey, 201584	24	28	1.2/mo	Blended	Blended	Yes (E)	Yes	Yes	Dietitian	NR	% weight loss Adverse events
Tapsell, 201786	12	7	0.58/mo	Blended	Individual	Yes (E)	Yes	Yes	Dietitian Exercise Physiologist Psychologist	Dietary pattern	% weight loss FBG BP
Teeriniemi, 201887	12	8	0.67/mo	In person	Blended	Yes (E)	Yes	Yes	Dietitian	NR	% weight loss WC FBG BP
Thomas, 201988	18	56	3.1/mo	In person	Group	Yes (E)	Yes	Yes	Dietitian Exercise Physiologist	Caloric restriction	% weight loss
Trepanowski, 201789	12	14	1.2/mo	In person	Individual	No	No	Yes	Dietitian	Caloric restriction	% weight loss FBG BP
Uemura, 201990	2	4	2/mo	In person	Blended	No	No	No	Dietitian Physician	Dietary pattern	BMI WC
van Gemert, 201591 van Gemert, 201592	2.5	13	5.2/mo	Blended	Blended	No	Yes	Yes	Dietitian	Caloric restriction Dietary pattern	QoL
Ventura Marra, 201993	3	12	4/mo	Remote	Individual	No	Yes	Yes	Dietitian	Caloric restriction Dietary pattern	% weight loss WC
Villareal, 201194	12	52	4/mo	In person	Group	Yes	Yes	Yes	Dietitian Physical therapist	Caloric restriction Modified macronutrient	QoL % weight loss
Vissers, 201096	12	12	1/mo	In person	Individual	Yes	No	No	Dietitian Physiotherapist	Caloric restriction	BMI WC FBG BP
Weinhold, 201597	4	16	4/mo	In person	Group	Yes (E)	Yes	No	Dietitian	Modified macronutrient	BMI % weight loss FBG BP

^kLITOE = Lifestyle Intervention Trial in Obese Elderly.

^aPA = physical activity.

^bDiets were categorized as “dietary patterns” if they were based on food types or groups, as opposed to nutrients or calories.

^cNR = not reported.

^dBMI = body mass index.

^eE = exercise group.

^fBP = blood pressure.

^gWC = waist circumference.

^hFBG = fasting blood glucose.

ⁱQoL = quality of life.

^jLEVA = Lifestyle for Effective Weight Loss During Lactation.

^lNEW = Nutrition and Exercise in Women.

^mSCOP = Saku Control Obesity Program.

Table 3 describes the summary of findings and rationale for certainty of evidence for each outcome. Table 4 provides results of sub-group analyses. Reasons for reducing certainty of evidence are documented in the summary of findings table (Table 3). The list of articles excluded during full-text review and reasons for exclusion can be found on the Evidence Analysis Library website.¹⁸ The most common reasons for exclusion were no intervention of interest (eg, not provided by a dietitian) or no adequate comparison group. Across outcomes, leave-one-out analysis demonstrated no meaningful effect of any one study. Publication bias is reported in funnel plots in Figure 4 (available at www.jandonline.org).

Table 3.

Summary of findings table describing effect of interventions provided by a dietitian for adults with overweight or obesity^a

Outcome/no. of participants (studies)	Anticipated absolute or relative effects (95% CI)	Risk of bias	Inconsistency	Indirectness	Imprecision	Other	Certainty12	What happens
BMIb No. of participants: 9,567 (38 RCTsc)26-28,30-35,40,42-44, 47,48,50-53,5 7,59,62, 64-68,70,71,76, 78,81-83,85,90,96,97	MDd 1.5 lower (1.74 lower to 1.26 lower)	↓e	↓f	⊖	⊖	↑↓g-j	⊕⊕⊕○ MODERATE	Adult weight management interventions provided by a dietitian likely result in a significantly reduced BMI
Percent weight loss No. of participants: 3,566 (22 RCTs)25,26,30,31,34,37, 40,50,52,53,63,67-69,71,77,85, 87-89,94,97	4.01% lower (5.26 lower to 2.75 lower)	↓	↓	⊖	⊖	↑ik	⊕⊕⊕⊕ HIGH	Adult weight management interventions provided by a dietitian resulted in significant percent weight loss.
5% Weight loss No. of participants: 7,586 (19 RCTs) 32,33,37,39,44,51, 52,56,59,60,63,67,71,81,83, 84,86,93,97	RRl 2.11 (1.30 to 3.41)	↓	↓	⊖	⊖	↑i	⊕⊕⊕○ MODERATE	Adult weight management interventions provided by a dietitian likely result in significantly increased proportions of participants who achieved 5% weight loss
Waist Circumference (cm) No. of participants: 8,707 (33 RCTs)26-28,30,31,33, 36,37,39,40,43,46,50,51,53,54, 56,59,61,64,65,68,71,76-78, 81,83,85,90,93,96,97	MD 3.45 cm lower (4.39 lower to 2.51 lower)	↓	↓	⊖	⊖	↑ik	⊕⊕⊕⊕ HIGH	Adult weight management interventions provided by a dietitian resulted in significantly reduced waist circumference (cm)
Systolic blood pressure (mm Hg) No. of participants: 3,852 (25 RCTs)25-28,30,31, 33,36,37,40,51,53,54,56,57,65, 70,71,76,77,81-83,96,97	MD 2.91 mm Hg lower (4.9 lower to 0.92 lower)	↓	↓	⊖	⊖	↑↓hjk	⊕⊕⊕○ MODERATE	Adult weight management interventions provided by a dietitian likely result in slightly but significantly reduced systolic blood pressure (mm Hg)
Diastolic blood pressure (mm Hg) No. of participants: 3,852 (25 RCTs)25-28,30,31,33,36, 37,40,51,53,54,56,57,65,70,71,76,77, 81-83,96,97	MD 1.99 mm Hg lower (3.02 lower to 0.96 lower)	↓	↓	⊖	⊖	↑↓hk	⊕⊕○○ LOW	Adult weight management interventions provided by a dietitian may result in slight significantly reduced diastolic blood pressure (mm Hg)
Fasting blood glucose (without diabetes) (mg/dLm) No. of participants: 2,537 (18 RCTs)26,27,33,37,43,56,65,67, 71,72,76,78,80-83,96,97	MD 1.37 mg/dL lower (2.75 lower to 0.01 higher)	↓	⊖	⊖	⊖	↑k	⊕⊕⊕⊕ HIGH	In adults with overweight or obesity but without diabetes, weight management interventions provided by a dietitian did not result in significant effects on fasting blood glucose
Fasting blood glucose (with type 2 diabetes) (mg/dL) No. of participants: 591 (2 RCTs)66,77	MD 12.47 mg/dL lower (17.5 lower to 7.44 higher)	↓	⊖	⊖	↓	↑i	⊕⊕⊕○ MODERATE	In adults with overweight or obesity but without diabetes, weight management interventions provided by a dietitian did not result in significant effects on fasting blood glucose
Quality of life-physical, assessed with: SF-36n No. of participants: 773 (5 RCTs)55,70,91,94,95	MD 5.8 higher (2.3 higher to 9.4 higher)	↓	↓	⊖	⊖	⊖	⊕⊕○○ LOW	Adult weight management interventions provided by a dietitian may result in significantly increased physical quality of life
Quality of life-mental, assessed with: SF-36 No. of participants: 773 (5 RCTs)55,70,91,94,95	MD 2.4 higher (1.55 higher to 3.23 higher)	↓	⊖	⊖	⊖	⊖	⊕⊕⊕○ MODERATE	Adult weight management interventions provided by a dietitian likely result in significantly increased mental quality of life
Cost-effectiveness No. of participants: 536 (2 RCTs)55,79	Not pooled	↓	⊖	⊖	↓	⊖	⊕⊕○○ LOW	Adult weight management interventions provided by a dietitian may be cost-effective for some adults with overweight or obesity

^aTable adapted from GRADEpro GDT: GRADEpro Guideline Development Tool.²³

^bBMI = body mass index; calculated as kg/m².

^cRCT = randomized controlled trial.

^dMD = mean difference.

^e↓ Indicates certainty of evidence was marked down for risk of bias, inconsistency, indirectness, or imprecision.

^f⊖ Indicates certainty of evidence was not marked up or down for the respective reason.

^g↑ Indicates certainty of evidence was marked up due to large effect size, dose-effect response, or other factors.

^hPublication bias suspected.

ⁱLarge effect size.

^jPlausible confounding would reduce demonstrated effect (eg, results from studies with high risk of bias).

^kDose—response gradient.

^lRr = relative risk.

^mTo convert mg/dL glucose to mmol/L, multiply mg/dL by 0,0555.

ⁿSF-36 = 36-Item Short Form Survey.

Table 4.

Results of sub-group analysis of adult weight management interventions provided by a dietitian according to intervention characteristics mean difference (95% CI)^a

Variable	BMIb (n = 38 RCTscd)	% Weight loss (n = 22 RCTs)	Waist circumference (cm) (n = 33 RCTs)	Systolic blood pressure (mmHg) (n = 25 RCTs)	Fasting blood glucosee (mg/dLf) (n = 18 RCTs)
mean difference (95% CI); no. of RCTs
In person or telehealth interventions vs controls
Exclusively in person	−1.71 (−2.05 to −1.38); 27	−3.59 (−5.20 to −1.99); 13	−3.60 (−4.57 to −2.64); 22	−4.67 (−6.89 to −2.45); 18	−1.20 (−2.38 to −0.02); 11
Exclusively remote	−0.82 (−1.34 to −0.30); 4	−5.17 (−7.73 to −2.61); 2	−1.94 (−3.72 to −0.15); 5	1.59 (−1.55 to 4.73); 5	−0.79 (−5.29 to 3.72); 4
Blended in person and remote	−1.16 (−1.45 to −0.87); 7	−4.56 (−6.24 to −2.89); 8	−3.60 (−5.22 to −1.98); 5	−1.67 (−3.81 to 0.46); 2	−2.74 (−4.85 to −0.63); 2
Individual or group interventions vs controls
Exclusively individual	−1.28 (−1.56 to −1.00); 18	−2.96 (−3.99 to −1.94); 11	−4.06 (−5.61 to −2.52); 15	−0.76 (−3.20 to 1.67); 12	−0.02(−2.12 to 2.07); 7
Exclusively group	−2.15 (−3.41 to −0.89); 6	−4.88 (−7.95 to −1.81); 5	−3.00 (−4.41 to −1.59); 4	−8.10 (−12.96 to −3.25); 6	−4.46 (−9.78 to 0.87); 3
Blended	−1.07 (−1.36 to −0.79); 12	−4.19 (−6.49 to −1.90); 7	−2.67 (−3.61 to −1.74); 14	−2.01 (−3.53 to −0.50); 7	−3.24 (−5.59 to −0.89); 8
Dietitian alone or as part of multidisciplinary interventions vs controls
Dietitian alone	−1.49 (−1.86 to −1.13); 19	−3.81 (−5.03 to −2.60); 16	−3.09 (−4.3 to −1.88); 19	−4.57 (−7.17 to −1.98); 12	−3.20(−6.19 to −0.21); 8
Multidisciplinary	−1.48 (−1.82 to −1.15); 20	−4.93 (−7.10 to −2.77); 7	−3.70 (−4.88 to −2.53); 13	−0.84 (−3.50 to 1.82); 12	−1.84 (−3.94 to 0.27); 10
No. of contacts with dietitian vs controls
1 to 4	−1.46 (−1.84 to −1.08); 13	−2.36 (−3.08 to −1.63); 3	−2.46 (−3.29 to −1.63); 4	−0.95 (−3.76 to 1.86); 3	0.31 (−7.56 to 8.18); 1
≥5	−1.55 (−1.88 to −1.22); 25	−4.23 (−5.71 to −2.74); 19	−3.63 (−4.67 to −2.59); 29	−3.34 (−5.58 to −1.10); 22	−1.44 (−2.86 to −0.01); 17
Frequency of contacts with dietitian vs controls
<1/mo	−1.96 (−2.93 to −0.99); 9	−3.39 (−4.79 to −1.98); 5	−2.75 (−5.08 to −0.42); 4	−2.45 (−5.59 to 0.69); 3	1.80 (−4.81 to 8.41); 1
1 to 3/mo	−1.38 (−1.66 to −1.10); 24	−4.26 (−6.25 to −2.26); 13	−3.85 (−4.97 to −2.74); 24	−3.53 (−6.45 to −0.62); 16	−1.16 (−2.61 to 0.29); 14
≥4/mo	−1.60 (−2.26 to −0.95); 6	−3.91 (−5.75 to −2.06); 5	−2.02 (−3.23 to −0.80); 5	−2.01 (−4.80 to 0.79); 6	−4.24 (−7.92 to −0.57); 3
Intervention study durations vs controls
<6 mo	−1.50 (−1.89 to −1.10); 14	−3.04 (−4.13 to −1.94); 7	−3.21 (−4.43 to −1.98); 10	−0.80 (−2.91 to 1.32); 7	−3.15 (−6.39 to 0.09); 5
6 to <12 mo	−1.11 (−1.56 to −0.67); 12	−4.57 (−8.06 to −1.09); 5	−2.81 (−4.71 to −0.92); 11	−4.11 (−8.56 to 0.33); 9	−0.59 (−3.61 to 2.42); 5
≥12 mo	−1.94 (−2.48 to −1.40); 12	−4.36 (−6.24 to −2.49); 11	−4.12 (−5.18 to −3.07); 12	−3.03 (−4.60 to −1.46); 9	−1.77 (−3.22 to −0.32); 8

^aAll results are compared with control groups. The outcomes of quality of life and cost-effectiveness were reported in too few studies for results to be stratified in sub-group analyses. Values in bold type indicate a statistically significant improvement compared with controls.

^bBMI = body mass index (calculated as kg/m²).

^cRCT = randomized controlled trial.

^dThe number of studies in the top row refers to the number of studies included in meta-analyses for that outcome. The number of studies for each sub-group analysis/outcome may not add up to the total number of studies if information was missing to categorize the study in the respective analysis or if a study included more than 1 intervention.

^eFor participants without type 2 diabetes.

^fTo convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555.

Figure 4.

Funnel plots describing publication bias of studies included in meta-analysis for the systematic review examining adult weight management interventions provided by a dietitian for adults with overweight or obesity. (A) Funnel plot for the outcome of body mass index. Egger’s statistic for publication bias z = −3.19; P = .0014. (B) Funnel plot for the outcome of percent weight loss. Egger’s statistic for publication bias: z = −0.79; P = .43. (C) Funnel plot for the outcome of waist circumference. Egger’s statistic for publication bias: z = −0.7272; P = .4670. (D) Funnel plot for the outcome of systolic blood pressure. Egger’s statistic for publication bias: z = −2.655; P = .0079. (E) Funnel plot for the outcome of diastolic blood pressure. Egger’s statistic: z = −2.543; P = .011. (F) Funnel plot for the outcome of fasting blood glucose. Egger’s statistic: z = −1.34; P = .182.

Risk of Bias

Inter-rater reliability between the first 2 independent assessments for the overall rating was 63% (agreement for 39 studies). The discrepancies in the remaining studies were often due to a difference in a sub-question of 1 domain. There was noteworthy risk of bias due to randomization throughout the Studies ^{26–29,31–33,37,38,41,42,44,47,48,51–55,59,62,65–70,75,77,80,82–84,86,87,89,90,92–94,96} primarily from lack of description of group allocation concealment from investigators until participants were assigned to groups. Many studies also demonstrated risk of bias due to deviations from the intended interventions ^{26–28,30,31,33,40,47,48,58,62,65–67, 74,77,79,86–88} However, risk of bias was low for missing outcome data, which included attrition bias, measurement of outcomes, and selection of the reported result in most studies (Figure 5).

Figure 5.

Risk of bias of included randomized controlled trials examining adult weight management interventions provided by a dietitian for adults with overweight or obesity and assessed using Version 2 of the risk-of-bias tool and the robvis tool.^19,24

Main Outcomes

BMI.

Forty RCTs reported the outcome of BMI^{26–28,30–35,40,42–44,47,48,50–53,57,59,60,62,64–68,70,71,76,78,81–83,85,90,92,96,97} and data for meta-analysis was available in all but 2 studies.^60,92 In meta-analysis of 38 RCTs, adult weight management interventions provided by a dietitian decreased BMI by an MD of −1.5 (95% CI −1.74 to −1.26) (Figure 6; available at www.jandonline.org). There was statistically significant heterogeneity in effect size between studies (I² = 94.6%; 95% CI 91.0% to 97.0%). These findings aligned with results of the 2 studies left out of the meta-analysis due to insufficient data available.^60,92 For the outcome of BMI, studies with high risk of bias resulted in smaller effects than studies with some concerns or low risk of bias in sensitivity analysis (data not shown). In adults with overweight or obesity, weight management interventions provided by a dietitian resulted in a statistically significant reduction in BMI with moderate evidence certainty.

Figure 6.

Forest plot for effect of adult weight management interventions provided by a dietitian on body mass index in adults with overweight or obesity.

Percent Weight Loss.

wenty-eight RCTs reported the outcome of percent weight loss as a continuous variable ^{25,26,30,31,34,37,40–42,50,52,53,63,65–69,71,77,84,85,87-89,92,94,97} and sufficient data from 22 RCTs were available for meta-analysis ^{25,26,30,31,34,37,40,50,52,53,63,67–69,71,77,85,87–89,94,97} in pooled analysis of 22 studies. interventions provided by a dietitian resulted in a statistically significant percent weight loss compared with control conditions (MD −4.01%; 95% CI −5.26% to −2.75%) (Figure 7; available at www.jandonline.org). Heterogeneity of results was high (I² = 96.6%; 95% CI 92.6% to 97.6%; P < .001). For 6 RCTs. data were insufficient to be included in meta-analysis, but all studies reported percent weight loss was greater in the intervention groups compared with the control groups.^{41,42,65,66,84,92} In adults with overweight or obesity, weight management interventions delivered by a dietitian resulted in a statistically significant percent weight loss with high evidence certainty.

Figure 7.

Forest plot for effect of adult weight management interventions provided by a dietitian on percent weight loss in adults with overweight or obesity.

Nineteen studies reported the number of participants in each group who achieved 5% weight loss and were pooled in meta-analysis.^{32,33,37,39,44, 51,52,56,59,60,63,67,71,81,83,84,86,93,97} participants in intervention groups had a risk ratio of 2.11 (95% CI 1.30 to 3.41; P < .01) for achieving 5% weight loss (they were more than twice as likely to achieve 5% weight loss). Heterogeneity of results was high (I² = 93.8%; 95% CI 75.2% to 94.9%) (Figure 8; available at www.jandonline.org). In adults with overweight or obesity, weight management interventions provided by a dietitian resulted in a statistically and clinically significant increase in proportion of participants who achieved 5% weight loss compared with controls with moderate evidence certainty.

Figure 8.

Forest plot for effect of adult weight management interventions provided by a dietitian on risk ratio of achieving 5% weight loss in adults with overweight or obesity.

WC.

Thirty-six RCTs reported the outcome of WC.^{26–28,30,31,33,34,36,37,39,40,43,46,50,51,53,54,56,59–61,64,65,68,71,76–78,81,83,85,90,92,93,96,97} Data for meta-analysis were available in all but 3 studies.^34,60,92 Meta-analysis of 33 RCTs resulted in a reduction in WC (MD −3.45 cm; 95% CI −4.39 to −2.51 cm) for adults receiving weight management interventions from a dietitian compared with control conditions (Figure 9; available at www.jandonline.org). Heterogeneity of results was high (I² = 92.7%; 95% CI 75.8% to 94.9%). These findings were aligned with results of the 3 studies not included in meta-analysis.^34,60,92 In adults with overweight or obesity, weight management interventions provided by a dietitian resulted in a statistically significant reduction in WC with high evidence certainty.

Figure 9.

Forest plot for effect of adult weight management interventions provided by a dietitian on waist circumference (cm) in adults with overweight or obesity.

Secondary Outcomes

Systolic Blood Pressure.

Blood pressure was reported in 28 RCTs,^{25–28,30,31,33,34,36,37,40,51,53,54,56,57,65,70,71,76, 77,81–83,86,89,96,97} and all but 3 of these studies were included in meta-analysis.^34,86,89 In meta-analysis of 25 RCTs, there was a reduction in systolic blood pressure (SBP) (MD −3.04 mm Hg; 95% CI −5.10 to −0.98 mm Hg) in intervention groups compared with the control groups (I² = 87.6%; 95% CI 70.1% to 92.6%) (Figure 10A; available at www.jandonline.org). In the studies not included in meta-analysis, there was no difference in SBP noted in 2 studies^34,89 and results were unclear in 1 study.⁸⁶

Figure 10.

Forest plot for effect of adult weight management interventions provided by a dietitian on (A) systolic blood pressure (mm Hg) and (B) diastolic blood pressure (mm Hg) in adults with overweight or obesity.

Diastolic Blood Pressure.

Twenty-six RCTs reported the outcome of diastolic blood pressure (DBP),^{25–28,30,31,33,34,36,37,40,51,53,54,56,57,65,70,71,76,77, 81–83,96,97} and all but 1 study reported data that could be pooled in meta-analysis.³⁴ In meta-analysis of 25 RCTs, there was a statistically significant reduction in MD for DBP of −1.99 mm Hg (95% CI −3.02 to −0.96 mm Hg) in the intervention groups compared with control groups (I² = 73.4%; 95% CI 73.3% to 93.8%) (Figure 10B; available at www.jandonline.org). There was no difference in DBP between groups in the study not included in meta-analysis.³⁴ Funnell plot and Egger’s statistic demonstrated some risk of publication bias (P = .011) (Figure 4; available at www.jandonline.org).

In adults with overweight or obesity, interventions delivered by a dietitian likely reduce SBP and DBP with moderate and low evidence certainty, respectively.

FBG.

Twenty-four included RCTs reported the outcome of FBG, ^{26,27,30,33,37,43,53,56,65–67,71,72,76–78,80–83,86,89,96,97} and all but 4 of these studies could be pooled in meta-analysis.^30,53,86,89 Two studies targeted adults with T2DM.^66,77 Al-Hamdan and colleagues,²⁶ Weinhold and colleagues,⁹⁷ and Parker and colleagues⁸⁰ targeted adults with prediabetes and overweight or obesity. In the study by Ma and colleagues,⁷¹ adult participants had pre-DM or metabolic syndrome, and in the study by Nilsen and colleagues,⁷⁶ adult participants were required to be at risk for T2DM using a diabetes risk score in addition to having overweight or obesity. In Rollo and colleagues,⁸¹ adult participants with overweight or obesity had recent gestational DM. Of these 6 studies targeting adults with diabetes risk and overweight or obesity, only Weinhold and colleagues⁹⁷ demonstrated a statistically significant reduction in FBG (MD −4.90 mg/dL [to convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555]; 95% CI −9.33 to −0.47 mg/dL) in the intervention group compared with the control group. In meta-analysis of 18 studies for adults without diagnosed diabetes and overweight or obesity, adult weight management interventions provided by a dietitian resulted in a statistically nonsignificant reduction in FBG compared with control conditions (MD −1.37 mg/dL; 95% CI 2.75 to 0.01 mg/ dL; I² = 41.7%; 95% CI 0.4% to 73.8%) (Figure 11; available at www.jandonline.org). In adults with overweight or obesity but without T2DM, weight management interventions provided by a dietitian did not result in statistically significant effects on FBG, and evidence certainty was high.

Figure 11.

Forest plot for effect of adult weight management interventions provided by a dietitian on fasting blood glucose (mg/ dL; to convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555) in adults with overweight or obesity.

Two RCTs targeted adults with overweight or obesity and T2DM and reported the outcome of FBG.^66,77 When results from these studies were pooled, there was a statistically significant reduction in MD for FBG in the intervention groups compared with the control groups (MD −12.47 mg/dL; 95% CI −17.50 to −7.44) (I² = 0%; 95% CI 0.0% to 78.8%). In adults with overweight or obesity and T2DM, weight management interventions provided by a dietitian resulted in reduced FBG and evidence certainty was moderate.

QoL.

Nine RCTs reported the outcome of QoL.^{44,55,61,70,81,86,91,94,95} Five of these studies used the 36-Item Short Form Survey (SF-36) to assess mental and physical QoL.^{55,70,91,94,95} The remaining 4 studies^44,61,81,86 used different tools, and 2 of these did not report data that could be used in meta-analysis.^61,86 Therefore, to calculate the MD in mental and physical QoL scores that may be more internally consistent and meaningful to practitioners compared with standardized MD, the 5 studies using the SF-36 were included in meta-analysis, and findings were compared with studies not included in the meta-analysis. In 5 RCTs, interventions provided by a dietitian resulted in an increased physical QoL score from the SF-36 (MD 5.8; 95% CI 2.3 to 9.4). Heterogeneity was high (I² = 94.4%; 95% CI 87.8% to 98.6%), and 3 studies demonstrated no effect of the intervention (Figure 12A; available at www.jandonline.org).^55,70,91 The interventions also resulted in increased mental QoL score (MD 2.39; 95% CI 1.55 to 3.23) assessed by the SF-36 and heterogeneity was low (I² = 12.3%; 95% CI 0.0% to 86.6%) (Figure 12B; available at www.jandonline.org).

Figure 12.

Forest plot for effect of adult weight management interventions provided by a dietitian on (A) physical quality of life and (B) mental quality of life using the 36-Item Short Form Survey.

Tapsell and colleagues⁸⁶ examined the outcome of QoL using the 12-Item Short Form Survey and found an impact of group assignment on physical, but not mental, median (interquartile range) scores. Hollis and colleagues⁶¹ used the Impact of Weight on Quality of Life-Lite tool and found a difference between groups in favor of the intervention. Rollo and colleagues⁸¹ found a very slight increase in QoL as measured by the Weight Efficacy Lifestyle Questionnaire, but De Vos and colleagues⁴⁴ found no effect of the intervention on EuroQoL score. In adults with overweight or obesity, evidence suggests that weight management interventions provided by a dietitian may result in a statistically significant increase in physical and mental QoL with low and moderate evidence certainty, respectively. Although some studies concluded a null effect, there were no studies that found negative effects of the interventions on QoL compared with controls.

Cost-Effectiveness.

Two studies reported the outcome of cost-effectiveness,^55,79 but reported cost-effectiveness in different ways that could not be pooled quantitatively. Hagberg and colleagues⁵⁵ reported cost-effectiveness of a 12-week intervention provided by a dietitian alone for postpartum women with overweight or obesity. The authors reported cost-effectiveness in terms of cost per gained quality-adjusted life-year. Cost was $229 for the intervention group and $5 for the control group. The likelihood of cost-effectiveness, or the proportion of patients who would find an intervention economically acceptable based on gain in quality-adjusted life-years ranged from 0.77 to 1.00, depending on the estimation tool used.^55,98

Padwal and colleagues⁷⁹ examined a multidisciplinary intervention lasting 3 months in duration. Cost estimate included initial development of in-person strategy and content. Study authors concluded that the per-patient cost of the intervention group was $278 compared with the control. Padwal and colleagues only reported follow-up data and there were no differences in outcomes between groups at follow-up.⁷⁹ Weight management interventions provided by a dietitian may be cost-effective for some adults who have overweight or obesity, but evidence certainty was low.

Adverse Events.

Seven RCTs reported adverse events.^{29,38,70,71,77,84,95} Anton and colleagues²⁹ reported no adverse events related to diet or exercise between groups. Campbell and colleagues³⁸ also reported no difference in musculoskeletal injuries from the exercise portion of the intervention between groups. However, bone mineral density was reduced in the intervention group compared with the control group. The LITOE (Lifestyle Intervention Trial in Obese Elderly) weight management trial included exercise in adults with obesity and resulted in exercise-related adverse events, such as pain and atrial fibrillation.⁹⁵ There were no adverse events reported in an mHealth intervention for 18- to 35-year-old participants.⁸⁴

Ma and colleagues⁷¹ evaluated adverse events from a diabetes prevention program for adults with T2DM and/ or metabolic syndrome, which included both nutrition and exercise. Four adverse events were reported, including 3 fractures and 1 syncopal episode during a group session.⁷¹ O’Neil and colleagues⁷⁷ also examined a Weight Watchers intervention led by a certified diabetes educator and dietitian for adults with T2DM and found more participants in the intervention group experienced hypoglycemia at 3 months (P < .001) and 6 months (P = .014), but not at 9 or 12 months. One incidence of hypoglycemia in the intervention group required hospitalization and was the only serious adverse event reported in the trial.⁷⁷

Liljensøe and colleagues⁷⁰ targeted adults before total knee replacement. Study authors noted some mild adverse events that may have been related to the low-energy diet, such as dry skin and gastrointestinal symptoms. In adults with overweight or obesity, weight management interventions provided by a dietitian may not result in serious adverse events. Minor diet-related events, such as dry skin or gastrointestinal symptoms, were noted infrequently. Evidence certainty was very low.

Sub-Group Analyses of Intervention Components

Results of sub-group analyses are summarized in Table 4.

In-Person or Telehealth Interventions.

Interventions delivered exclusively in-person resulted in a statistically significant improvement in all 5 outcomes for which sub-group analyses were conducted compared with controls, including BMI, percent weight loss, WC, SBP, and FBG (Table 4). Interventions delivered exclusively with telehealth had a smaller effect size than interventions delivered in person compared with controls for the outcomes of BMI (MD −0.82; 95% CI −1.34 to −0.30 for telehealth interventions vs MD −1.71; 95% CI −2.05 to −1.38 for in-person interventions) and WC (MD −1.94 cm; 95% CI −3.72 to −0.15 cm for telehealth interventions vs MD −3.60 cm; 95% CI −4.57 to −2.64 cm for in-person interventions). Interventions delivered exclusively with telehealth did not result in statistically significant improvement in SBP (MD 1.58 mm Hg; 95% CI −1.55 to 4.73 mm Hg vs MD −4.67 mm Hg; 95% CI −6.89 to −2.45 mm Hg for in-person interventions) or FBG (MD −0.79 mg/dL; 95% CI −5.29 to 3.72 mg/dL for telehealth interventions vs MD −1.20 mg/ dL; 95% CI −2.38 to −0.02 mg/dL for in-person interventions) compared with controls. There was overlap in CIs between intervention groups for some outcomes (Table 4). Results from hybrid interventions were more similar to those delivered in-person than to those delivered exclusively remotely (Table 4).

Individual or Group Interventions

Interventions delivered in both the individual and group settings combined resulted in statistically significant improvement compared with controls (Table 4). Interventions delivered exclusively in a group or exclusively individually did not result in improved FBG levels compared with controls (MD −0.02 mg/dL; 95% CI −2.12 to 2.07 mg/dL for exclusively individual vs MD −4.46 mg/dL; 95% CI −9.78 to 0.87 for exclusively group vs MD −3.24 mg/dL; 95% CI −5.59 to −0.89 for blended). In addition, interventions delivered exclusively individually did not result in a statistically significant improvement in SBP compared with controls (MD −0.76 mm Hg; 95% CI −3.20 to 1.67 mm Hg for exclusively individual vs MD −8.10 mm Hg; 95% CI −12.96 to −3.25 mm Hg for exclusively group vs MD −2.01 mm Hg; 95% CI −3.53 to −0.50 for blended) (Table 4).

Dietitian Alone or Multidisciplinary Intervention

All interventions included a dietitian, but some interventions included additional health professionals. Effect sizes were similar between intervention types for anthropometric outcomes (eg, effect on BMI was MD −1.49; 95% CI −1.86 to −1.13 for interventions from a dietitian alone vs MD −1.48; 95% CI −1.82 to −1.15 for multidisciplinary interventions), but interventions provided by a dietitian alone had a greater improvement on SBP (MD −4.57 mm Hg; 95% CI −7.17 to −1.98 mm Hg for interventions from a dietitian alone vs MD −0.84 mm Hg; 95% CI −3.50 to 1.82 mm Hg for multidisciplinary interventions) and FBG (MD −3.20 mg/dL; 95% CI −6.19 to −0.21 mg/dL) for interventions from a dietitian alone vs MD −1.84 mm Hg; 95% CI −3.94 to 0.27 mm Hg for multidisciplinary interventions) compared with controls, although CIs overlapped for these outcomes (Table 4).

Number of Contacts with the Dietitian

Interventions including at least 5 contacts with the dietitian had a larger effect size, compared with controls, than interventions with 4 or fewer contacts (eg, effect on percent weight loss was MD −2.36%; 95% CI −3.08% to −1.63% for interventions with 4 or fewer contacts and MD −4.23%; 95% CI −5.71% to −2.74% for interventions with 5 or more contacts, effect on SBP was MD −0.95 mm Hg; 95% CI −3.76 to 1.86 mm Hg for interventions with 4 or fewer contacts and MD −3.34 mm Hg; 95% CI −5.58 to −1.10 mm Hg for interventions with 5 or more contacts, and effect on FBG was MD 0.31 mg/dL; 95% CI −7.56 to 8.18 mg/dL for interventions with 4 or fewer contacts and MD −1.44 mg/dL; 95% CI −2.86 to −0.01 mg/dL for interventions with 5 or more contacts). However, there was overlap in CIs for these outcomes (Table 4).

Frequency of Contacts with the Dietitian

There were no clear dose-response patterns between frequency of contacts with the dietitian and effect sizes, except for FBG, for which greater frequency resulted in a greater effect size, compared with controls, than lower frequency interventions (MD −4.24 mg/dL; 95% CI −7.92 to −0.57 mg/dL for interventions with a frequency 4 or more times/month vs MD 1.80 mg/dL; 95% CI −4.81 to 8.41 mg/dL for interventions with a frequency fewer than 1 time/month), although CIs overlapped (Table 4).

Study Duration

For nearly every outcome examined, studies that were at least 12 months in duration resulted in the largest effect size compared with controls (eg, effect on BMI was MD −1.50; 95% CI −1.89 to −1.10 for interventions less than 6 months vs MD −1.94; 95% CI −2.48 to −1.40 for interventions ≥12 months in duration), although there was overlap in CIs (Table 4). Studies less than 12 months did not result in statistically significant improvement of SBP or FBG compared with controls (Table 4).

DISCUSSION

This systematic review aimed to assess the effect of weight management interventions provided by a dietitian compared with usual care or no intervention, on a variety of cardiometabolic outcomes and QoL in adults with overweight or obesity. A total of 73 articles,^25–97 representing 62 RCTs, were included in this systematic review. Compared with controls, adult weight management interventions provided by a dietitian likely reduced BMI; increased percent weight loss; increased likelihood of participants achieving at least a 5% weight loss; reduced WC; likely reduced SBP and DBP; may increase QoL; may be cost-effective for some clients; and may not result in serious adverse events, although data for cost-effectiveness and adverse events was extremely limited and therefore uncertain.

These findings agree with other recent and relevant systematic reviews. A 2019 systematic review concluded dietitian-led interventions for adult weight management in the primary care setting were effective in reducing BMI. However, only 4 studies were included in meta-analysis and the effect size was smaller (MD −0.43; 95% CI −0.59 to 0.26) than in the current systematic review.⁹ A 2020 systematic review from the US Preventive Task Force examined the effect of behavioral counseling for adults with cardiovascular disease risk, including but not limited to those with overweight or obesity, and found a beneficial effect of the intervention on anthropometric outcomes with high heterogeneity.⁹⁹ Effect sizes for BMI (MD −0.5; 95% CI −0.7 to −0.3) and WC (MD −1.8 cm; 95% CI −2.4 to −1.1) were smaller in the 2020 systematic review compared with the current review, likely because all adult participants did not have overweight or obesity. The current systematic review adds to this literature by providing evidence of the efficacy of a wide variety of interventions provided by dietitians for adults with overweight or obesity in a variety of settings. Although interventions resulted in statistically significant improvements for nearly all outcomes examined, the effect sizes were not always clinically significant. This does not necessarily indicate that interventions provided by a dietitian do not meaningfully improve these parameters, but instead may indicate that results are heterogeneous within and between studies. This heterogeneity is likely due to several factors, such as skills of the dietitian, stage of change of the client, quality of collaboration between the dietitian and client, and intervention adherence. Different intervention approaches, such as group contacts, may be beneficial for some adult participants but not others.¹⁰⁰ In addition, intervention success may depend on factors such as social support, ability to exercise, or medications affecting weight status.^101,102 It is essential for dietitians to tailor treatment and recommendations based on each client’s individual factors, such as culture, sociodemographic factors, and personal life circumstances.^103–105 Because of the complex and variable nature of lifestyle interventions, it may not be valid to ascertain an “absolute” improvement in effect size for all adult weight management interventions combined.

This systematic review attempted to determine which intervention components may increase efficacy by conducting sub-group analyses according to predetermined intervention components. Although the relative effect size was not always consistent, patterns emerged across outcomes. For example, although interventions that were 12 months in duration improved all outcomes, those of a shorter duration did not improve SBP and FBG compared with controls. Indeed, studies have suggested that dietitian support may maximize retention and results in long-term weight loss studies.¹⁰⁶ More research is needed to identify the optimal duration for weight management interventions for adults with overweight or obesity.

This systematic review found both individual and group contacts to be efficacious in improving a variety of outcomes. However, a hybrid of group and individual contacts for adult weight management interventions resulted in a statistically significant improvement in all outcomes assessed. Providing both individual contacts as well as support groups may contribute different benefits and prove to provide the most efficacious results in practice. Interestingly, Renjilian and colleagues¹⁰⁷ found that group contacts, despite participant preference, led to the most pronounced reductions in weight and body mass. However, very few studies comparing these types of components or using a combination of components exist, and further research is warranted. This systematic review found that both in-person and virtual contacts provided improved results for a variety of outcomes. These results provide essential information as the COVID-19 era has moved the health care field to provide more telehealth services. Indeed, recent studies have highlighted the efficacy of telehealth and web-based weight loss interventions.¹⁰⁸ In addition, Ross and colleagues¹⁰⁹ found that individuals younger than 65 years preferred videoconferencing interventions to in-person contacts. Practitioners may also find it useful to use a blended or hybrid format for contacts that incorporates both in-person and virtual contacts. One recent study found that a hybrid model of in-person and virtual contacts led to easier access for patients across a wide spectrum of backgrounds and also improved the cost-effectiveness of the program.¹¹⁰ Comparing efficacy of in-person vs telehealth contacts will be important to investigate further as ease, affordability, and access improve and facilitate population-based overweight and obesity treatment interventions.

This systematic review found that adult weight management interventions provided by a dietitian resulted in improved outcomes for several cardiometabolic parameters, and there is some evidence of cost-effectiveness compared with standard care. Collectively, these results strengthen data to support reimbursement for dietitian contacts in treatment for overweight and obesity in adults.

Limitations

There are some limitations to the current systematic review. Although 73 articles were included, many weight management interventions were excluded based on a priori criteria and there was limited evidence available to evaluate effectiveness on the outcomes of QoL and cost-effectiveness. In addition, due to the need to prioritize outcomes, some important intermediate outcomes, such as blood lipid profile, were not included in this systematic review. The results of this systematic review evaluate the effect directly after the intervention and do not capture data published on outcomes at follow-up time points either for assessment only or extended care. In addition, data from “grey literature,” including government and private industry publishers, and studies published before 2008, were not included; thus, results may not be reflective of the full breadth of research addressing the research question. Heterogeneity of results was high, which may reduce overall confidence in the effect estimate. However, recognition of this heterogeneity and examination of potential contributors, such as intervention components, is a strength of this systematic review.¹¹¹ Risk of bias was common throughout included studies, contributing to reduced certainty of evidence for some outcomes.

Future Research

It is essential to gather further data on patient outcomes from practicing dietitians to allow for further elucidation of the impact of adult weight management interventions on cardiometabolic parameters. There is a need for further research to assess the impact of different intervention components and strategies on outcome efficacy. Maintaining weight loss can be challenging, and more information is needed regarding effect of extended care contacts with dietitians on outcomes. Research and practicing dietitians can collaborate to plan, intervene, and collect data that will be translatable and applicable for dietetics practitioners.

CONCLUSIONS

This systematic review demonstrated that dietitians play a crucial role in improving cardiometabolic outcomes and potentially improving QoL for adults with overweight or obesity, although evidence certainty varied by outcome. Weight management interventions provided by a dietitian are effective for treating overweight and obesity in adults. Because of the high prevalence of overweight and obesity, and the health and economic burden associated with consequences of overweight and obesity, dietitians provide a crucial service for improving public health. Sub-group analyses demonstrated some influence of intervention components, but heterogeneity of results precludes firm conclusions. Thus, dietitians should individualize intervention components to the needs and preferences of each adult client.

Supplementary Material

Figures 2, 4, 6, 7, 8, 9, 10, 11, and 12 are available at www.jandonline.org

RESEARCH SNAPSHOT.

Research Question:

In adults with overweight or obesity, what is the effect of weight management interventions provided by a registered dietitian or international equivalent compared with usual care or no intervention on cardiometabolic outcomes?

Key Findings:

This systematic review included 62 randomized controlled trials. Results demonstrated that interventions provided by a registered dietitian or international equivalent resulted in statistically significant improvements in body mass index (−1.5), percent weight loss (−4.01%), and waist circumference (−3.45 cm in adults with overweight or obesity. Evidence certainty for these outcomes was moderate to high. A wide variety of interventions resulted in improved anthropometric outcomes.