Primary, Secondary, and Tertiary Prevention of Metabolic Syndrome: A Narrative Literature Review and Resource for Chiropractors

Abstract

Objective

The objective of this review is to summarize current information for chiropractors on Metabolic Syndrome (MetS) related to prevention and health promotion.

Methods

Research staff and faculty of a doctor of chiropractic program performed a narrative review, which included guidelines from the United States Preventative Task Force and meta-analyses. We performed a PubMed search of meta-analyses published in English between 2019 to 2024, indexed with the Medical Subject Heading “Metabolic Syndrome,” and which had free-text availability. Meta-analyses were included if they were relevant to chiropractic practice and health promotion/prevention.

Results

The PubMed search resulted in 156 citations of which 38 meta-analyses were selected for inclusion in this review. Clinical intervention strategies identified that may reduce MetS risk and negative sequelae include screening for MetS, such as measuring waist circumference, blood pressure and biomarker levels. In addition, chiropractors can support lifestyle behavior changes that may help patients lose weight such as increasing protein intake from plant-based diets, increasing physical activity, optimizing sleep and reducing sugar-sweetened beverage consumption.

Conclusions

This review summarizes current information on MetS related to prevention and health promotion. Chiropractors and other health care professionals knowledgeable of the lifestyle-related risk factors associated with MetS can use this information to better screen and manage at-risk patients.

Introduction

Metabolic Syndrome (MetS) is when a patient meets several criteria that put them at high risk for diabetes, as well as cardiovascular disease, the leading cause of years of life lost globally.¹ In a systematic review of global MetS prevalence, the most commonly used criteria for identifying MetS were from the International Diabetes Foundation published in 2006.^2,3 These are highlighted in Figure 1. The estimated global adult prevalence of MetS is between 12.5% and 31.4%, with higher estimates in the Eastern Mediterranean and Americas regions and in upper-middle to high income countries.² Some demographic groups are more at risk than others,⁴ such as people living in urban environments,² adults without a high school education,^5,6 night shift workers,⁷ and people with lower household incomes.⁶

Fig 1.

Criteria for metabolic syndrome from the International Diabetes Foundation.

By 2030, there will be an estimated shortage of 10.2 million health care workers to address MetS and other chronic health conditions.⁸ Chiropractors may be able to help address this shortage, especially in the United States (US) where there are 23.7 chiropractors for every 100 000 people.⁹ The World Federation of Chiropractic states that chiropractors support healthy diet/nutrition¹⁰ and physical activity.¹⁰ In 2021, a clinical practice guideline was published with evidence-based recommendations for doctors of chiropractic (DC) to integrate health promotion into their practices.¹¹ While not specific to MetS, several of the recommendations may reduce the burden of MetS as well as the burden of spinal pain, which is frequently addressed by chiropractors.12, 13, 14 These recommendations include: Screening for lifestyle-related disease risk factors such as diet, lack of physical activity, and tobacco use; Identifying overweight or obese patients and “asking permission to initiate a health-focused and person-centered discussion with them”; ^11(p.11) Providing affordable and culturally appropriate nutrition guidance for adults of all body sizes; and Advising patients to “reduce sitting time and increase moderate-to-vigorous physical activity.”^11(p.11)

According to a survey of US Chiropractic Licensing Boards, it is within the scope of practice for chiropractors to analyze blood tests (example, fasting blood glucose and glycated hemoglobin (HbA1c)); provide life-style counseling, diet information and vitamin supplementation; and to perform blood pressure testing in the majority of states.¹⁵ Nearly a third of US chiropractors encounter patients with diabetes/MetS on a daily basis and approximately 50% of chiropractors co-manage patients with diabetes/MetS more than 50% of the time.¹⁶ Based on US Council on Chiropractic Education Accreditation Standards, all chiropractors should be minimally competent to “evaluate(s) the patient’s health status for the purpose of constructing a differential diagnosis, directing clinical decision-making,... and determine[ing] the need for emergency care, referral, and/or collaborative care.”^17(p.19-20) Furthermore, chiropractic college curricula should include classes that teach physiology, pathology, biochemistry, laboratory diagnosis, and nutrition.^17(p.2) These classes are fundamental to chiropractors in diagnosing and managing patients with risk factors for MetS and its sequelae. The objective of this manuscript is to provide updated information on MetS for the practicing chiropractor, based on national guidelines and meta-analyses with a focus on prevention and health promotion.

Methods

In February 2023, faculty and research staff at a Doctor of Chiropractic program met to discuss ideas for improving intern management of patients with MetS and to gather related resources students may receive in their academic courses prior to entering clinic, such as guidelines from the United States (US) National Institutes of Health,¹⁸ US Department of Agriculture and US Department of Health and Human Services,¹⁹ American Heart Association,²⁰ and US Preventative Task Force.21, 22, 23, 24, 25 This process led to identifying a need for additional references to guide interns in evidence-based case management of patients with MetS.

A PubMed search was performed for meta-analyses published in English between January 2019 and January 2024 with open access availability and indexed with the Medical Subject Heading “Metabolic Syndrome.” Titles were screened for relevance to chiropractors in promoting MetS prevention with adult patients before MetS develops (primary prevention); screening for early MetS identification (secondary prevention); and managing MetS to reduce negative sequelae (tertiary prevention).²⁶ Studies were excluded if the focus was not prevention, the population was pediatric, and the intervention was medical or not something typically taught in chiropractic schools.

After excluding studies that were determined not relevant to MetS prevention in chiropractic practice, the remaining studies from the PubMed search underwent full text review. The authors individually read the manuscripts and decided that some studies were not useful for MetS prevention in chiropractic practice. The primary reason for exclusion after full-text review was that the study did not demonstrate a positive change in MetS biomarkers. Details from the remaining studies were extracted into Google Sheet (Google LLC, 2006) and further edited in Excel (Microsoft Corporation, 2024). Data extraction included first author last name and location; publication year; and PICO elements (P = population of interest, I = intervention or exposure, C = comparison; O = primary outcome(s)). Table 1 also describes the study designs included in the meta-analyses, the key findings (measures of association, 95% confidence intervals) and number of studies included in the meta-analyses. A synthesis was prepared beginning with secondary prevention practices followed by primary and tertiary prevention approaches. Primary and tertiary were combined into 1 section since the majority of studies did not differentiate between incidence (new) MetS cases and prevalence (existing) MetS cases.

Table 1.

Extracted Data From 38 Meta-Analyses That Address Primary, Secondary or Tertiary Metabolic Syndrome Prevention

Study	Location of First Author	Study Designs Included in Meta-Analyses	Population (P). Intervention/Exposure (I). Control (C). Outcome (O).	Level of Prevent-ion	Measure of Association (95% Confidence Interval CI); Number of Studies in Analysis; I2 Statistic for Heterogeneity
Amirani et al.27	Kashan University of Medical Sciences, Iran	RCTs	P: Patients with metabolic syndrome and related disorders. I: Whey protein. C: Placebo, carbohydrate supplementation, usual diet or no intervention. O: Glycemic control and serum lipoproteins.	3°	HbA1c Weighted Mean Difference (WMD): −0.15 (95% CI: −0.29, −0.01); 6 studies; I2 = 91%. Triglyceride (TG) WMD: −17.12 (95% CI: −26.52, −7.72); 22 studies; I2 = 92%. High Density Lipoprotein (HDL): non-sig.
Bakaloudi et al.28	Aristotle University of Thessalonik, Greece	Observational	P: General population and patients with chronic conditions including MetS. I: High adherence to Mediterranean Diet. C: Low adherence to MD. O: HDL, triglycerides, waist circumference, fasting blood glucose, and systolic blood pressure.	1° or 3°	TG Standardized Mean Difference (SMD): −0.29 (95% CI: −0.52, −0.05); 27 high quality studies; I2 = 97%. HDL SMD: 0.36 (95% CI: 0.03, 0.68); 25 high quality studies; I2 = 98%.
Che et al.29	Tianjin Medical University, China	Cohort	P: 18-95 year olds. I/C: Sleep duration. O: MetS incidence.	1°	Short sleep (<6 h) Odds Ratio (OR) = 1.15 (95% CI: 1.09-1.22); 13 studies; I2 = 52%. Long sleep (>8 h) OR = 1.19 (95% CI: 1.05, 1.35); 12 studies; I2 = 71%.
Chen et al.30	Wuhan University School of Basic Medical Sciences, China	Cohort and cross-sectional	P: Ages 1-84 I/C: Second-Hand Smoke (SHS) Exposure. O: MetS parameters.	1° or 3°	27-74 year olds: Fasting Plasma Glucose WMD = 1.38 mg/dL (95% CI: 0.07, 2.68); 6 studies; I2 = 0%. Waist Circumference WMD = 1.75cm (95% CI: 0.3, 3.2); 5 studies; I2 = 44%.
Chen et al.31	Zhejiang University School of Medicine, China	Clinical trials	P: Patients with MetS I: eHealth (phone-based care, web-based interactive lifestyle modification programs). C: Usual care or wait-listed. O: MetS parameters.	3°	BMI SMD: −0.36 (95% CI: −0.61, −0.10); 6 studies; I2 = 65%. Waist circumference SMD: −0.30 (95% CI: −0.49, −0.10); 6 studies; I2 = 32%. SBP (SMD: −0.35 (95% CI: −0.55, −0.04); 6 studies; I2 = 66%.
Cheng et al.32	Qingdao University, China	Observational	P: Adults. I/C: Dietary Calcium intake. O: MetS diagnosis.	1° or 3°	Highest vs. lowest dietary Calcium intake OR: 0.80 (95% CI: 0.70, 0.91); 15 studies; I2 = 52%.
Choi et al.33	Sungshin Women’s University, Seoul, Korea	RCTs	P: Adults with chronic conditions. I: L-carnitine. C: No intervention. O: MetS parameters.	3°	WC MD: −1.89 (−3.14, −0.64); 2 studies; I2 = 28%. SBP MD: −7.41 (−14.59, −0.23); 2 studies; I2 = 0%. No significant effects for FBS, TG, and HDL.
Companys et al.34	Unitat de Nutrició i Salut, Spain	Prospective cohort and RCTs	P: People with cardiovascular risk factors I/C: High and low fermented dairy food & probiotic consumption. O: Incidence of cardiovascular disease & mortality, obesity, type 2 diabetes, MetS.	1°	MetS RR (Yogurt): 0.80 (0.74, 0.87); 3 studies; I2 = 0%. Triglycerides SMD (Probiotics): −0.45 (−0.75, −0.14); 3 studies; I2 = 0%. Waist circumference SMD (Probiotics): −0.37 (−0.52, −0.21); 12 studies; I2 = 53%. Fasting blood glucose SMD (Probiotics): −0.28 (−0.45, −0.12); 10 studies; I2 = 39.6%.
Dludla et al.35	South African Medical Research Council, South Africa	RCTs	P: Adults with MetS. I: CoQ10. C: Placebo. O: Adipokine function including markers of inflammation and lipid peroxidation.	3°	HbA1c SMD: −0.65 (95% CI: −1.27, −0.03); 3 studies; I2 = 75%.
Fakhr et al.36	Tabriz University of Medical Sciences, Iran	RCTs	P: Adults (healthy or with type 2 diabetes). I: Fenugreek consumption. C: Matched control group. O: MetS parameters.	1° or 3°	FPG WMD: −16.75 mg/dL (95% CI: −23.36, −10.15); 21 studies; I2 = 99%. TG SMD: −20.12mg/dL (95% CI: −34.24, −5.60); 17 studies; I2 = 99%. HDL WMD: 3.55mg/dL (95% CI: 1.98, 5.12); 17 studies; I2 = 93%. WC WMD: −2.51(95% CI: −3.78, −1.24); 3 studies; I2 = 16%. SBP WMD: −3.45mmHg (95% CI: −6.38, −0.52); 6 studies; I2 = 93%. Non-significant effects on DBP and BMI.
Fu et al.37	China Academy of Chinese Medical Sciences, China	RCTs	P: Adults. I: Garlic, Garlic derivatives, or garlic extracts. C: Placebo. O: MetS parameters.	3°	WC SMD: −0.78 (95% CI: −1.09, −0.47); 3 studies; I2 = 0%. TG SMD: −0.66 (95% CI: −1.23, −0.09); 15 studies; I2 = 90%. DBP SMD: −1.33 (95% CI: −2.14, −0.53); 9 studies; I2 = 92%. SBP SMD: −0.56 (95% CI: −1.58, 0.47); 9 studies; I2 = 95%. HDL and FBG non-significant.
Gea et al.38	Universidad Miguel Hernández, Spain	Clinical trials	P: Adult workers. I: Diet, food and nutrition-based work-based interventions. O: MetS parameters.	3°	WC MRAW: −2.06 (95% CI: −2.98, −1.13); 17 studies; I2 = 81%. BMI MRAW: −0.86 (95% CI: −1.2, −0.51); 19 studies; I2 = 95%. HDL MRAW: 0.83 (9% CI: 0.07, 1.59); 19 studies; I2 = 50%. TG MRAW: −12.0 (95% CI: −18.69, −5.31); 17 studies; I2 = 65%. SBP MRAW: −3.39 (95% CI: −5.92, −0.86); 20 studies; I2 = 96%. DBP MRAW: −2.89 (95% CI: −3.93, −1.84); 20 studies; I2 = 89%. Moderator analysis found increase BMI, SBP and DBP with basic education and general counseling.
Gobin et al.39	Nanjing Medical University, China	Cross-sectional, case-control, cohort	P: Adults. I/C: Periodontal disease diagnosis. O: MetS diagnosis.	2°	Adjusted OR: 1.45 (95% CI: 1.31, 1.61); 32 studies; I2 = 74%.
Guo et al.40	Inner Mongolia Autonomous Region Academy of Traditional Medicine, China	RCTs	P: Patients with MetS. I: Chitosan. C: Placebo. O: Glycemic levels.	3°	Fasting Glucose SMD: −0.39mmol/L (95% CI: −0.62, −0.16); 14 studies; I2 = 76%. HbA1c SMD: −1.10 (95% CI: −2.15, −0.06); 4 studies; I2 = 94%.
Han et al.41	Zhejiang Provincial Center for Disease Control and Prevention, China	Cross-sectional and cohort	P: Adults. I/C: Different doses of dietary calcium. O: MetS diagnosis.	1° or 3°	RR: 0.89 (95% CI: 0.80, 0.99); 10 studies; I2 = 75%. RR (Females only): 0.74 (95% CI: 0.66, 0.83); 5 studies; I2 = 0%. RR (each 300 mg/d increase: 0.93 (95% CI: 0.87, 0.99); 8 studies; I2 = 77%.
Hu et al.42	Southeast University, Nanjing, China	Cohort and cross-sectional	P: Adults. I/C: Sleep hours and sleep quality. O: MetS diagnosis.	1° (cohort results)	RR < 6 h: = 1.14 (95% CI: 1.10, 1.19); 8 cohort studies; I2 = 79%. RR > 8.5 h: 1.15 (1.09, 1.23); 7 cohort studies; I2 = 76%. Sleep quality OR/RR: 1.46 (1.03, 2.06); 8 studies; I2 = 78.3% (Sub-analysis of cohort studies sleep quality not-significant).
Jin and Je43	Kyung Hee University, Korea	Cohort and cross-sectional	P: Adults. I/C: Highest/lowest dairy products consumption. O: MetS diagnosis.	1° (cohort results)	Cohort studies dose-response RR (400 g/d total dairy): 0.71 (95% CI: 0.59, 0.85); 6 studies; I2 = 72%. RR (200 g/d milk): 0.85 (95% CI: 0.79, 0.93); 5 studies; I2 = 52%. RR (200 g/d yogurt): 0.63 (95% CI: 0.53, 0.75); 5 studies; I2 = .3%. RR (50 g/d cheese) non-signifiant.
Kim et al.44	Keimyung University, Korea	RCTs	P: 18-65 year olds. I: Technology-mediated interventions (web-based resources, video consultation, text messages etc). C: No treatment, usual care, other non-tech interventions. O: MetS parameters.	1° or 3°	Waist circumference SMD = −0.35 (95% CI: −0.54, −0.15); 11 studies; I2 = 60%. Fasting Glucose SMD: −0.31 (95% CI: −0.42, −0.19); 8 studies; I2 = 0%. Triglycerides SMD: −0.14 (95% CI: −0.26, −0.03); 11 studies; I2 = 0%. SBP SMD = −0.25 (95% CI: −0.37, −0.14); 11 studies; I2 = 44%. DBP SMD: = −0.32 (95% CI: −0.51, −0.13); 11 studies; I2 = 58%.
Liang et al.45	Home For The Aged Guangzhou, China	RCTs	P: Adults with high MetS and cardiovascular risk factors. I: Aerobic, resistance, and combined exercise. C: Non-exercised controls. O: MetS parameters.	3°	Glucose MD (Combined exercise vs control): - 8.46 (95% CI: −13.78, −5.14); 8 studies. TG MD (Combined exercise vs control): −20.39 (95% CI: −12.03, −28.74); 9 studies. Glucose and TG levels were also lower comparing combined exercise with aerobic and resistance groups.
Mardi et al.46	Alborz University of Medical Sciences, Iran	Cohort and cross-sectional	P: Children and adults. I/C: LDL-C, non-HDL-c and atherogenic index. O: MetS diagnosis.	2°	non-HDL-Cholesterol MetS (Adults) OR: 3.53 (95% CI: 2.29, 4.78); 5 studies; I2 = 72%.
Mena-Sánchez et al.47	Universitari Sant Joan de Reus, Spain	Cohort	P: Adults. I/C: Dairy product consumption. O: MetS diagnosis.	1°	RR (Highest/lowest total dairy): 0.73 (95% CI: 0.64, 0.83); 9 studies; I2 = 62%. RR (low fat dairy): 0.77 (95% CI: 0.65, 0.91); 2 studies; I2 = 89%. RR (Yogurt): 0.74 (95% CI: 0.66, 0.82); 4 studies; I2 = 0%. RR (whole milk dairy) non-significant.
Merida et al.48	Universidad Aut´onoma de Madrid, Spain	Cross-sectional	P: Humans. I/C: levels of urine phthalate metabolites. O: MetS diagnosis.	1° or 3°	MetS OR (high molecular weight phthalates) = 1.11 (95% CI: 1.07, 1.15); 7 low-risk of bias studies; I2 = 10%.
Munoz-Cabrejas et al.49	Hospital Universitario Miguel Servet, Spain	Cohort and cross-sectional	P: Adults. I/C: Sugar sweetened beverage consumption levels. (High vs Low). O: MetS diagnosis.	1° or 3°	OR (cross-sectional): 1.35 (95% CI: 1.15, 1.58); 13 studies; I2 = 57%. OR (cohort): 1.18 (95% CI: 1.06, 1.32); 7 studies; I2 = 70%.
Papadaki et al.50	University of Bristol, UK	Controlled trials	P: Adults. I: Mediterranean Diet. C: No treatment, usual care, or different diet advice. O: MetS parameters, MetS incidence, MetS related morbidity and mortality.	1° and 3°	Cardiovascular Disease RR: 0.61 (95% CI: 0.42, 0.80); 2 studies; I2 = 0%. Stroke RR:0.67 (95% CI: 0.35, 0.98); 2 studies; I2 = 0%. SBP MD: −1.34 (95% CI: −2.00, −0.67); 27 studies; I2 = 94%. HDL MD: 1.30 (95% CI: 0.38, 2.21); 36 studies; I2 = 98%. Glucose MD: −2.98 (95% CI: −4.54, −1.42); 31 studies; I2 = 98%. Triglycerides MD: −12.30 (95% CI: −15.60, −8.99); 38 studies; I2 = 95%. WC MD: −1.47 (95% CI: −2.54, −0.39); 27 studies; I2 = 99.6%.
Peiris et al.51	La Trobe University, Australia	RCTs	P: Adults with MetS. I: Diet and unsupervised exercise lifestyle intervention programs. C: Usual Care. O: MetS parameters.	3°	WC MD: −2.29 cm (95% CI: −3.26, −1.32); 4 studies; I2 = 0%. SBP MD: −3.89 mmHg (95% CI: −5.19, −2.58); 7 studies; I2 = 4%. DBP: −3.16 mmHg (95% CI: −4.83, −1.49); 6 studies; I2 = 50%. Non-significant results for TG, HDL-c and Fasting Glucose.
Qiu et al.52	China Academy of Chinese Medical Sciences, China	RCTs	P: MetS patients. I: Curcumin. C: Placebo or blank O: Metabolic, inflammatory, and oxidative stress markers.	3°	WC MD: −2.16 (95% CI: −3.78, −0.54); 7 studies; I2 = 0%. Fasting Blood Sugar MD: = −8.6 (95% CI: −15.45, −1.75); 9 studies; I2 = 71%. HDL MD: = 4.98 (95% CI: 2.58, 7.38); 8 studies; I2 = 71%. DBP MD: −2.8 (95% CI: −4.53, −1.06); 5 studies; I2 = 40%. Non-significant results for SBP, TG.
Ramli et al.53	Universiti Sultan Zainal Abidin, Malaysia	RCTs	P: Adults 18-70 with MetS. I: Coffee (Caffeinated and decaf) and Green Coffee Extract. C: VariedO: MetS parameters.	3°	Caffeinated coffee Fasting Glucose MD: 0.17 (95% CI: 0.09, 0.25); 2 studies; I2 = 22%. Green Coffee Extract WC MD: −0.39 (95% CI; −0.68, −0.10); 4 studies; I2 = 93%. Green Coffee Extract TG MD: −0.27 (95% CI: −0.43, −0.10); 5 studies; I2 = 89%. Green Coffee Extract HDL MD: 0.62 (95% CI: 0.34, 0.90); 6 studies; I2 = 91%. Green Coffee Extract SBP MD: −0.44 (95% CI: −0.57, −0.32); 3 studies; I2 = 27%. Green Coffee Extract DBP MD: −0.83 (95% CI: −1.40, −0.26); 3 studies; I2 = 91%.
Raya-Cano et al.54	University of Córdoba, Spain	Cross-sectional, case-control and cohort	P: Adults. I: Uric Acid. C: No MetS. O: MetS.	2°	Uric acid in men with and without MetS MD: 0.53 (95% CI: 0.45, −0.62); 17 studies; I2 = 97%. Uric acid in women with and without MetS MD: 0.57 (95% CI: 0.48, 0.66); 15 studies I2 = 97%.
Semnani-Azad et al.55	University of Toronto, Canada	Cohort	P: Children and adults. I/C: Levels of dietary fructose consumption. O: MetS incidence.	1°	Sugar sweetened beverages RR: 1.21 (95% CI: 1.06, 1.31); 7 studies; I2 = 68%. Yogurt RR: 0.83 (95% CI: 0.77, 0.90); 5 studies; I2 = 1%. Fruit RR: 0.91 (95% CI: 0.89, 0.93); 4 studies; I2 = 0%. Non-significant associations for honey, ice cream, and confectionary. Non-linear dose responses for mixed and 100% fruit juice.
Serrablo-Torrejon et al.56	School of Health and Life Sciences, UK	RCTs	P: Adults with MetS. I: High Intensity Interval Training. C: No exercise. O: MetS parameters.	3°	BG MD: −0.11 (95% CI: −0.16, −0.06); 8 studies; I2 = 75%. SBP MD: −4.44 (95% CI: −6.83, −2.06); 6 studies; I2 = 57%. DBP MD: −3.60 (95% CI: −5.43, −1.78); 6 studies; I2 = 45%. WC MD −2.26 (95% CI: −3.12, −1.40); 9 studies; I2 = 49%.
Sooriyaar-achchi et al.7	Queensland University of Technology, Australia	Cross-sectional and cohort	P: Health Sector Workers. I: Shift work. C: Standard Day work. O: MetS Diagnosis.	1° or 3°	OR = 2.17 (95% CI: 1.31, 3.60); 12 studies; I2 = 82%
Ulloque-Badaracco et al.57	Universidad Peruana De Ciencias Aplicadas, Peru	Cross-sectional, case-control, cohort	P: Adults. I/C: apolipoprotein (Apo) levels. O: MetS diagnosis.	2°	Case-Control results: ApoB levels and MetS OR: 3.20 (95% CI: 1.43, 7.19); 6 studies I2 = 91%. ApoB/ApoA ratio and MetS OR: 6.98 (95% CI: 5.72, 8.53); 4 studies; I2 = 20%.
Ulloque-Badaracco et al.58	Universidad Peruana De Ciencias Aplicadas, Peru	Cross-sectional, case-control, cohort	P: Adults. I/C: Vitamin B12, Folate, and Homocysteine levels. O: MetS diagnosis.	2°	B12 MetS OR: 0.89 (95% CI: 0.81, 0.93); 22 studies; I2 = 90%. Homocysteine MetS OR: 1.19 (95% CI: 1.14, 1.24); 61 studies; I2 = 90%. Folate levels non-sig.
Willems et al.59	University of Groningen, Netherlands	RCT	P: Adults with average BMI > 30. I/C: Macronutrient composition, caloric intake, and/or weight loss. O: MetS parameters.	3°	SBP WMD (Low-carbohydrate, 12 mo): −4.7 (95% CI: −6.1, −3.4); 6 studies. SBP WMD (Low-fat, 12 mo): −2.7 (−3.8, −1.5); 6 studies. Fasting glucose WMD (Low-fat, 12 mo): −0.12 (−0.18, −0.05); 6 studies. Changes remained statistically significant with body weight change as moderator but not with caloric intake as moderator. See figure 4 of Willems study for summary of all findings.
Yi et al.60	Zhejiang University, China	Cross-sectional and cohort	P: General population. I/C: Dietary inflammatory index. O: MetS parameters.	1° (cohort results)	Cohort: Abdominal obesity OR: 1.37 (95% CI: 1.19,1.57); 3 studies; I2 14%. High blood pressure OR: 1.27 (95% CI: 1.08, 1.50); 3 studies; I2 = 20%. Hyperglycemia OR: 1.17 (95% 1.10, 1.25); 3 studies I2 = 0%. TG (OR: 1.26 (95% CI: 1.03, 1.54); 3 studies; I2 = 37%.
Zhang et al.61	Beijing Center for Disease Prevention and Control, China	Cross-sectional	P: Adults. I/C: Serum ferritin levels. O: MetS diagnosis and MetS parameters.	2°	OR (high quality studies only) MetS: 1.72 (95% CI: 1.59, 1.87); 11 studies; I2 = 54%. OR (abdominal obesity): 1.42 (95% CI: 1.24, 1.62); 8 studies; I2 = 53%. OR (FPG): 1.84 (95% CI: 1.50, 2.25); 8 studies; I2 = 78%. OR (TG): 2.09 (95% CI: 1.72, 2.54); 8 studiesI2 = 76%. OR (HDL): 1.33 (95% CI: 1.19, 1.49); 8 studies; I2 = 44%.
Zhang et al.62	Guizhou Medical University, China	Cross-sectional, case-control and cohort	P: Adults and children. I/C: Levels of Sugar-sweetened beverages, artificial sweetened beverages and total sweetened beverage. O: MetS diagnosis.	1° (cohort results)	Cohort results: Total Sugar Sweetened Beverages RR: 1.56 (95% CI: 1.32, 1.83); 15 studies; I2 = 76%. Sugar Sweetened Beverages RR (adults): 1.15 (95% CI: 1.07, 1.24); 6 studies; I2 = 7%. Artificial Sweetened Beverages RR (adults): 1.34 (95% CI: 1.15, 1.56); 3 studies; I2 = 52%.
Zou et al.63	Guangzhou Sport University, China	RCTs	P: Adults. I: Wuqinxi exercise. C: Active or inactive control. O: MetS parameters.	1° or 3°	SBP SMD: 0.62 (95% CI: 0.38, 0.85); 6 studies; I2 = 24%. DBP SMD: 0.62 (95% CI: 0.22, 1.00); 5 studies; I2 = 61%. TC SMD: 0.87 (95% CI: 0.49, 1.24); 6 studies; I2 = 67%. HDL SMD: 0.95 (95% CI: 0.43, 1.46); 6 studies; I2 = 82%.

1°, primary prevention, preventing MetS from developing; 2°, secondary prevention, early MetS detection; 3°, tertiary prevention, reducing negative sequelae from MetS; BMI, body mass index; CI, confidence interval; DBP, diastolic blood pressure; FBG/FPG, fasting blood/plasma glucose; g, grams; HbA1c, glycosylated hemoglobin; HDL, high density lipoprotein; I2, statistic for heterogeneity; MD, mean difference; mmHg, millimeter of mercury; MRAW, raw, untransformed, mean; OR, odds ratio; RCTs, randomized controlled trials; RR, risk ratio; SBP, systolic blood pressure; SMD, standardized mean difference; TG, triglyceride; WC, waist circumference; WMD, weighted mean difference.

Results

The PubMed search resulted in 156 titles. Of these, 61 (40%) underwent full text review and 38 (24%) were selected for data extraction.

Secondary Prevention Screening for MetS

The US Preventive Services Task Force (USPSTF) suggests screening all adults over the age of 40 and those at risk of hypertension (example BMI ≥ 25), at least once a year.²² For adults aged 18 to 39 who are not at risk of hypertension and had a prior normal screening, the screening may be conducted every 3-5 years.²² A meta-analysis published in 2021 found a 9% reduction of major cardiovascular events with 5 mm Hg reductions in Systolic Blood Pressure (SBP).⁶⁴

For pre-diabetes and diabetes, the USPSTF recommends screening adults ages 35 to 70 who have a BMI ≥ 25.²¹ The American Diabetes Association recommends screening adults of all ages with BMI ≥ 25 and one or more risk factor such as first degree relative with diabetes, physical inactivity and hypertension.⁶⁵ Screening tests may include fasting plasma glucose (FPG) or HbA1c levels or an oral glucose tolerance test.²¹ The suggested frequency is every 3 years.²¹

The American Association of Clinical Endocrinologists and American College of Endocrinology recommends dyslipidemia screening, including HDL-C, annually for adults older than 65 and every 1 to 2 years for middle-aged adults (Men 45-65; Women 55-65).⁶⁶ Earlier and more frequent testing is recommended for adults with presence of atherosclerotic cardiovascular disease risk factors such as smoking, hypertension, diabetes, and obesity.⁶⁶

In addition to screening for the MetS criteria highlighted in Figure 1, there are other secondary prevention strategies that may be used to help screen patients with or at risk of MetS. Several biomarkers are associated with MetS in addition to fasting glucose, HbA1c, triglyceride and HDL levels. When ordering labs, chiropractors may also want to include checking for elevated non-high-density lipoprotein cholesterol levels (associated with a 3 times greater odds of MetS diagnosis);⁴⁶ serum ferritin (which can alter the insulin-receptor signaling pathway);⁶¹ apolipoprotein B (which may enhance formation of arterial blood clots and plaques);⁵⁷ homocysteine (due to its effect on endothelia damage which leads to inflammation and cardiovascular disease);⁵⁸ and uric acid (which induces oxidative stress on endothelial cells making them produce less nitric oxide, a vasodilator).⁵⁴ While lab value thresholds may vary according to the assay used,⁵⁸ the following are the normal reference ranges provided by the American Board of Internal Medicine: Non-high-density lipoprotein (optimal < 100 mg/dL); Serum Ferritin (24-307 ng/mL for males, 24-336 ng/mL for females); Apolipoprotein B (<90 mg/dL); Homocysteine (5-15 μmol/L); Serum Uric Acid (3-7 mg/dL).⁶⁷

Primary Prevention (Preventing MetS From Developing) and Tertiary Prevention (Reducing Negative Sequelae From MetS)

Weight Loss

Weight loss can improve MetS.⁵⁹ Losing 5% of body weight is generally considered a clinically important change²⁵ and the USPSTF recommends providers offer or refer their adult patients with body mass indexes >30 kg/m² to intensive weight-loss lifestyle behavioral interventions that combine dietary changes and increased physical activity.^23,25 Interventions vary in their frequency and content, but typically involve 6 hours of contact time (in-person or delivered remotely) over 6 to 18 months and include motivational interviewing and behavioral change techniques, such as goal setting, problem solving, and self-monitoring.^23,24 The consensus of over 60 DCs is that brief interventions (3-10 minutes, potentially spread over multiple visits) can be used in chiropractic practice to help adult patients with risk factors of chronic disease make lifestyle behavior changes.¹¹ These interventions should identify the patient’s willingness to change, provide information and resources that are easily accessible to the patient (including being at the appropriate level of health literacy) and agree on a specific change that is meaningful to the patient within their cultural values.¹¹ When chiropractors communicate with patients about weight, it is important they use neutral rather than stigmatizing words. Adult patients prefer “weight” and “BMI” over “obesity,” “fatness,” “large size” and “excess fat.”⁶⁸ In a technology-driven world, providers can integrate web-based resources, telephone/video consultation, text message, email, etc. to support patient compliance with weight reduction.^44,31 Work-place interventions promoting physical activity with coaching are more effective than those providing just lifestyle and healthy habit information.³⁸

Physical Activity

Physical activity may reduce the burden of MetS. Physical activities range from traditional Chinese Medicine Wuqinxi movements⁶³ to high intensity interval training.⁵⁶ Clinicians can help their patients increase their physical activity by providing patient education, facilitating goal setting, and encouraging self-monitoring.⁵¹ Pedometers are an example of a self-monitoring tool that may be useful as step counts are inversely associated with MetS.⁶⁹ The prescribed exercise does not need to be supervised to have some beneficial effect⁵¹ and exercise that combines aerobic and resistance exercise will have a greater impact on MetS than either type of exercise on its own.⁴⁵ The USPSTF recommends counseling adults at risk of cardiovascular disease to achieve 90 to 180 minutes per week of moderate to vigorous activity.²³ Resistance exercise should consist of single-set exercises that use the major muscle groups 2 to 3 times per week.⁷⁰ Prior to prescribing exercise, the 2023 health promotion clinical practice guideline for chiropractors recommends screening currently sedentary patients for signs/symptoms of cardiovascular/metabolic/renal disease and then, after medical clearance, beginning light to moderate intensity exercise.¹¹

Diet

Both low refined carbohydrate (LC) and low saturated fat diets (LF) can help achieve weight loss and reduce MetS components.⁵⁹ LC diets have less than 40% of the total energy intake from carbohydrates and LF diets have less than 30% of the energy intake from fats.⁵⁹ Both LC and LF diets increase the percentage of energy derived from protein, and for every 2.9% increase in the proportion of energy derived from protein, there is approximately 1 kg (2.2 lb) lowering of body weight.⁵⁹ Not all protein sources are equivalent, however, and the American Association of Clinical Endocrinology recommends plant-based diets to reduce cardiovascular disease and Type 2 diabetes risks.⁷⁰ Low-fat dairy and yogurt may be especially beneficial as they are associated with decreased incidence of MetS.34, 43, 47, 55 A possible mechanism for yogurt, as described by Mena-Sánchez et al.,⁴⁷ is calcium’s role in decreasing fat absorption and blood pressure and the anti-inflammatory properties of probiotics. This is supported by 3 meta-analyses in our literature review that found inverse relationships between MetS and either dietary calcium^{41, 32} or probiotics.³⁴

The Mediterranean diet is one recommended plant-based diet with approximately 35% to 45% of daily energy from fats, 35% to 45% from carbohydrates, and 15% to 18% from protein. It offers a wide assortment of potential choices from various food sources, including whole grains, legumes, fish, vegetables, fruit, nuts, and extra virgin olive oil.^28,71 According to a 2021 meta-analysis, high adherence to the Mediterranean diet (compared to low adherence) is specifically associated with lower triglyceride levels and higher concentration of HDL.²⁸ A 2020 meta-analysis of controlled clinical trials comparing the Mediterranean diet to no treatment, usual care, or a different diet found the Mediterranean diet was associated with a 39% reduced risk of cardiovascular disease and 33% reduced risk of stroke, however, there was not a statistically significant difference in risk of cardiovascular mortality or Type 2 Diabetes incidence. According to the study authors, this is likely attributable to heterogeneity of included studies since “effect estimates for most of these outcomes favored the Mediterranean Diet.”⁵⁰ Cohort studies also provide evidence for the association of reduced odds of MetS with low-inflammatory diets like the Mediterranean diet.⁶⁰ While the Mediterranean diet often includes red wine, we cannot justify recommending any levels of alcohol due to the risks it has for cancer and overall mortality.⁷²

The dietary approaches to stop hypertension (DASH) is another meal pattern that promotes whole grains, legumes, vegetables, fruits, and nuts, and also includes low-fat or fat-free dairy products.⁷¹ DASH consists of 27% of dietary energy from fats, 55% from complex carbohydrates and 18% from protein. It emphasizes reduced sodium (1500-2300 mg/d); high fiber (>30g/d) and limited saturated fat (6% of total daily energy).⁷¹ The DASH diet is associated with 2 to 5 mm Hg reduced systolic and 1.5 to 3.5 mm Hg reduced diastolic blood pressure,^73,74 as well as lowered body weight, BMI, waist circumference and triglyceride levels (but no statistically significant effect on glucose levels).⁷⁴

Supplements

One in 4 chiropractors supply nutritional supplements, herbs, enzymes or homeopathic remedies to their patients on a daily basis as an adjunctive treatment.¹⁶ A previous narrative review in the Journal of Chiropractic Medicine described the potential role of supplements on insulin sensitivity.⁷⁵ Several meta-analyses from the current PubMed search documented improvements in one or more MetS components with supplement use; specifically for probiotic capsules/powder,³⁴ Trigonella foenum-graecum (fenugreek),³⁶ Coenzyme Q_10,⁶² whey protein,²⁷ green coffee extract,⁵³ curcumin,⁵² garlic supplementation,³⁷ L-carnitine,³³ B-12⁵⁸ and chitosan.⁴⁰ Chiropractors who recommend supplements for their patients must be prudent in following national regulations on food and supplement claims. For example, in the US, regulations prohibit companies or people from making claims that specific foods or supplements prevent, treat, or cure a disease without approval from the Food Drug Administration (FDA) on making a health claim.⁷⁶ Any claim that a nutritional product benefits the body’s structure or function must also include a disclaimer that “This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease” (Brody, 2016 as cited by Avery et al, 2017).⁷⁶

Sugar Sweetened Beverages (SSB)

Patients should be encouraged to reduce intake of SSB, including sugar-sweetened soft drinks, fruit juices, energy drinks, and milkshakes, as these all may increase MetS risk.^55,62,49 Involvement with local task forces and coalitions to implement sales taxes on SSB may also be warranted, as a 2022 meta-analysis by Andreyeva et al.⁷⁷ found SSB taxes reduce SSB sales by 15% (95% CI: −9%, −20%).⁷⁷ More research is needed, however, on the health effects of SSB taxes.

Tobacco and Second Hand Smoke

Tobacco use and second hand smoke are both associated with MetS components.^66,30 Chiropractors can help their patients with tobacco cessation⁷⁸ as well as work with their communities to reduce SHS exposure through policy change.⁷⁹

Sleep

Chiropractors should recommend that patients get no less than 7 hours nor greater than 9 hours of sleep each night.^42,29 They should also consider using a validated tool for measuring sleep outcomes, such as the Pittsburgh sleep quality index (PSQI),⁸⁰ which is a brief self-reporting questionnaire documenting qualitative sleep parameters and sleep disturbances. Shift workers have been shown to experience a greater risk of MetS⁷ and chiropractors may also consider helping these patients to institutionalize the following work-related changes: making nutritious food available late at night; offering biannual health screenings for MetS; regulating shift schedules; and providing workplace interventions that improve sleep quality.^7,81,82

Environmental Interventions and Advocacy

Addressing environmental risk factors may be managed through legislative changes rather than individual or institutional changes.⁸³ For example, the US 2008 “Consumer Product Safety Improvement Act” and the European Union 2020 “Registration, Evaluation, Authorization and Restriction of Chemicals” legislation both restrict potential exposure to phthalates which are associated with elevated MetS risk.⁴⁸

It is important to recognize that adopting recommended lifestyle behavior changes may be easier for some populations than others, and that chiropractors serve the patients in their practice as well as serving the wider community. A 2019 meta-analysis found 15% greater odds of MetS (95% CI: 1.12, 1.18) for people with economic and social vulnerability.⁴ In the US, approximately 1 in 20 households experiences very low food security with prevalence increasing between 2020 and 2022.⁸⁴ Individuals in these households may go without any food, and a lack of resources may prohibit the ability to follow nutritional advice. One solution that has been found to increase fruit and vegetable intake in vulnerable populations is mobile produce markets. The success of these are influenced by policies such as street permits and acceptance of food assistance program benefits.⁸⁵ When advocating for policy changes, it may be helpful to point out the economic costs of MetS in addition to the clinical and public health burdens. For example, studies have found medical costs for individuals with MetS are 1.5 to 3 times those for individuals without MetS and that costs increase for each additional MetS component.86, 87, 88

Discussion

This paper provides a synthesis of findings that chiropractors and other healthcare providers can apply to their practice by working directly with adult patients, referring to other health care specialists, or joining with community members to create health policy changes. This narrative synthesis incorporates findings from the PubMed search described above as well as US national guidelines.

An educational infographic aimed at chiropractic clinicians, and a two page infographic and education page aimed at chiropractic patients are provided in the supplementary file.

Strengths and Limitations

A strength of this manuscript is the focus on evidence from recent systematic reviews with meta-analyses and current national guidelines. While the national guidelines were from US institutions, all 35 of the meta-analyses included in Table 1 had first authors located in another country.

A primary limitation is the study design was a narrative literature review. A systematic approach was taken to identify the meta-analyses, but additional resources were gathered informally. Unlike a systematic review, the included studies were not thoroughly critically appraised for bias using a tool such as the AMSTAR2 checklist.⁸⁹ It is important to note that several of the meta-analyses included data from cross-sectional studies which limits causal inference. Also, many focused on statistically significant changes in surrogate outcome measures, which may not translate into clinically significant reductions in morbidity and mortality.^90,91 High heterogeneity was also noted in several of the meta-analyses. While the I² statistic for heterogeneity was included in Table 1, the authors of this narrative review did not assess how the variability of studies within the meta-analyses may have biased the results.

Additional limitations include the potential bias in the selection of meta-analyses and the lack of dual assessment for study inclusion and data extraction. Only open access studies published in English were included and the search strategy was restricted to a narrow time frame of publication (2019-2024) and one database (PubMed). Some interventions may have evidence for reducing the population burden of MetS but were not included in this manuscript because they were not found in the limited search strategy. Furthermore, this study did not attempt to summarize the evidence for what is known to not be effective at preventing MetS.

While our review identified prevention strategies for the general adult population that are likely to be seen by DCs in a typical chiropractic practice, we did not delve deeply into more specific needs of individual patients that may be addressed using specialized clinical protocols within chiropractic practice and/or referrals to other clinical specialists. For instance, given an association between periodontitis and MetS,³⁹ chiropractors may consider screening their patients who present with oral health problems for MetS as well as referring such MetS patients to oral health specialists. Patients with chewing difficulties, food allergies/intolerances, or other compromised abilities to consume nutritious food may benefit from referral to oral health and nutrition specialists.

Conclusion

Chiropractors frequently encounter patients with MetS. The information synthesized in this review provides a resource which may help the time-pressed clinician better screen and manage patients identifiable as at-risk for MetS. Due to the high prevalence of MetS and its negative effects on population morbidity and mortality, it is very important that chiropractors contribute to primary, secondary, and tertiary prevention of this condition through appropriate screening, patient education, health advocacy, and interdisciplinary collaboration. Additional research is needed to identify evidence for interventions not captured by this study's search strategy.

Funding Sources and Conflicts of Interest

No funding sources or conflicts of interest were reported for this study.