Abstract
Objective:
To examine 1) the association between weight loss and changes in health-related quality of life (HRQoL), and 2) treatment response heterogeneity among patients in a weight loss intervention.
Methods:
Eighteen primary care clinics were randomized to a 24-month intensive lifestyle intervention or usual care. HRQoL and weight-related QoL were assessed at baseline and months 6, 12, and 24. Associations were analyzed using repeated measures linear multi-level models.
Results:
The sample included 803 patients with obesity. Changes in HRQoL did not differ by race or sex, and weight-related QoL did not differ by sex. However, Black patients experienced less improvement in weight-related QoL compared to other races. There was a graded association between improvements in weight-related QoL and greater weight loss between baseline and 24 months: 7.4 (95% CI: 5.1, 9.7) for those who lost <5% of their initial body weight, 15.0 (11.4, 18.5) for 5-<10% weight loss, and 18.9 (15.4, 22.4) for ≥10% weight loss. Greater weight loss was also related to greater improvements in most HRQoL domains.
Conclusions:
Weight loss was associated with improvements in HRQoL, and race differences were identified in changes in weight-related QoL, highlighting the need for precision medicine approaches to weight loss.
Keywords: well-being, treatment effect heterogeneity, patient-reported outcomes
Introduction
Health-related quality of life (HRQoL) refers to an individual’s perceptions of their wellbeing in relation to their culture and value systems, with an emphasis on health status.1–3 Self-reported measures of HRQoL are positively associated with survival among patients with heart failure4 and several cancers,5, 6 in addition to a reduced risk of premature mortality in the general population.7 Measures of HRQoL are also negatively associated with the body mass index (BMI) and obesity.2, 8 HRQoL can be measured by using instruments that focus on generic (non-disease specific) HRQoL or more obesity-specific HRQoL domains, and the relationship between weight loss and HRQoL may differ with respect to these two types of HRQoL assessment.
Given that approximately 40% of the U.S. adult population has obesity,9 the health benefits of weight loss beyond the scale are important to consider. Interventions that promote weight loss could potentially improve HRQoL and are important from a public health perspective. While the cardiometabolic health benefits of weight loss are well known,10–12 less is known about changes in HRQoL associated with weight loss, especially in the context of lifestyle interventions. For example, in an umbrella review of 12 meta-analyses, HRQoL showed consistent improvements following bariatric surgery, and although there was evidence for improvements in HRQoL following non-surgical weight loss, the results were not as consistent.2 Additionally, prior studies show heterogeneity of treatment effects across subgroups, including race and sex, in response to clinical trials for weight loss.13, 14 An early examination of weight loss results by race from two randomized trials (the Hypertension Prevention Trial and the Trials of Hypertension Prevention) reported that black men and women lost 1.4 kg to 2.7 kg less weight compared to white men and women.14 Similarly, the Promoting Successful Weight Loss in Primary Care in Louisiana (PROPEL) trial, the source of the data for the present study, found that percent weight loss among Black patients was at least one percentage point less than among patients of other races at 24 months of follow-up.13 These results have been identified in other intensive interventions as well (i.e., Diabetes Prevention Program, DPP;15 Action for Health in Diabetes, Look AHEAD16). The proposed mechanisms underlying observed racial differences in weight loss include differences in behavioral, socioeconomic, cultural, and biological (physiology, metabolism) factors.13, 14 Sex differences in weight loss were examined in a review of 49 studies which found that eleven studies (22%) reported sex differences, ten of which showed greater weight loss among men than women, postulated to be related to body composition and other physiological differences.17 However, authors cautioned that due to sample size and unbalanced sex proportions many of the studies may have had low power to detect sex differences. 17
The purpose of this study was to examine the effects of a high-intensity lifestyle intervention on weight-related and generic HRQoL among patients with obesity. Additionally, this study responds to a call-to-action2 which highlighted the need for research focused on potential gradients in QoL change by amount of weight loss and interactions with variables, including sex and race. This study uses data from the PROPEL cluster-randomized trial12, 13 in which patients with obesity in Louisiana primary care clinics were randomized to either a 24-month intensive lifestyle intervention (ILI) or usual care (UC) group. Prior studies demonstrated that during the PROPEL trial, patients in the ILI experienced considerably greater overall weight loss, a higher percentage of patients achieving clinically significant weight loss (e.g., at least 5%), and improvements in cardiometabolic parameters compared to UC.12, 13 However, the impact of the PROPEL intervention on HRQoL outcomes have not yet been examined in detail.
Methods
Study Design and Participants
The primary aim of the PROPEL trial was to test the effectiveness of a pragmatic, high intensity lifestyle-based obesity treatment program delivered within primary care clinics. Trial design details and primary outcome findings were previously published.13, 18, 19 PROPEL was conducted between April 2016 and September 2019. Louisiana primary care clinics (N=18) serving predominantly low-income populations were randomized to either a 24-month ILI or UC group. A total of 803 patients (n=451 intervention) enrolled in the trial. Inclusion criteria included an age of 20 to 75 years, BMI between 30 and 45 kg/m2, and being a patient of a participating clinic. Patients were excluded from participation if they were currently taking weight loss medication or participating in a weight loss program, had lost more than 10 lbs in the past year, had bariatric surgery in the past, or were planning to have bariatric surgery in the next two years. The protocol was approved by the Pennington Biomedical Research Center Institutional Review Board, and all patients provided written informed consent prior to participation.
Intensive Lifestyle Intervention
Patients received a health-literacy appropriate high-intensity lifestyle weight loss intervention, which was based on previous behavioral lifestyle programs including the Diabetes Prevention Program,20 the LOOK AHEAD study,21 and CALERIE study22 interventions and was consistent with the 2013 American Heart Association/American College of Cardiology/The Obesity Society Guidelines.23 All materials and approaches were adapted to be health-literacy and culturally appropriate through extensive consultation with our Patient Advisory Boards and health literacy experts (T.D. and C.A.).
The intervention was delivered in weekly sessions by health coaches embedded in the clinics (16 face-to-face and 6 via phone) during the first 6 months, and at least monthly face-to-face or phone sessions for the remaining 18 months for a total of 43 sessions.18 During the initial 6 months, patients were coached to lose 10% of their initial body weight, followed by weight loss maintenance for the remaining 18 months. Patients and health coaches worked on goal setting and developing and adhering to customized diet and physical activity action plans. Session topics included using portion-controlled foods and meal replacements, increasing physical activity, self-monitoring, structured diets, healthy snacking, and dealing with stress.
Usual Care
Enrolled patients in UC clinics received their normal, usual care from their primary care team throughout the 24-month period. While the UC group was not required to see their primary care practitioner (PCP) for weight management counseling, they were provided with a series of health-related newsletters to help engage and retain them in the study. The PCPs in UC clinics received a baseline presentation which described weight management in primary care settings and the current Centers for Medicare and Medicaid Services (CMS) approach to reimbursing for obesity treatment.24 An informational brochure on the CMS approach to reimbursing for obesity treatment was sent to the PCPs at least once per year throughout the trial.
Anthropometry
Anthropometric data were collected at baseline and months 6, 12, and 24 of follow-up by trained assessment technicians who were blinded to intervention group. Fasting body weight was measured in duplicate with the patient in light clothing without shoes using a digital scale (Seca Model 876). Height was measured in duplicate using a portable stadiometer (Seca Model 213), and the BMI was calculated (weight (kg) / height (m2)).
Generic Health-Related Quality of Life
Generic HRQoL was measured at 6, 12, and 24 months of follow-up using the 29-item Patient-Reported Outcomes Measurement Information System (PROMIS-29)25 inclusive of seven domains each with 4 questions and a raw score ranging from 4 to 20: physical function, anxiety, depression, fatigue, sleep disturbance, ability to participate in social roles and activities, and pain interference. The PROMIS-29 also includes an additional pain intensity item for which patients rate their pain from 0 to 10. Previous studies found that the PROMIS scales were reliable and valid measures of generic quality of life symptoms compared to legacy measures (e.g., SF-36, PHQ-9, GAD-7, etc.).26, 27 Raw scores were T-score standardized using the HealthMeasures Scoring Service (https://www.assessmentcenter.net/ac_scoringservice). Higher scores reflect better HRQoL for physical function and social functioning, and lower scores reflect better HRQoL for the remaining domains. The interpretation of PROMIS-29 change scores is as follows: improvement from baseline is indicated by positive change scores for physical function and social functioning while negative change scores indicate improvement from baseline for anxiety, fatigue, pain interference, pain intensity, depression, and sleep disturbance.
Weight-Related Quality of Life
Weight-related QoL was assessed at baseline and 6, 12, and 24 months of follow-up using the Impact of Weight on Quality of Life – Lite (IWQOL-L) questionnaire which is designed to measure obesity-specific aspects of HRQoL. The IWQOL-L showed moderate-to-high reliability (α-reliability coefficients > 0.75) among a sample of adults undergoing obesity treatment and that 14% of the variance in IWQOL-L total score was attributable to weight loss.28 Studies testing the measure’s psychometrics concluded that the instrument is a reliable and valid measure of obesity-specific quality of life.28, 29 The IWQOL-L produces a total score and scores for 5 component domains: physical function/functional capacity (11 items), self-esteem (7 items), sexual life (4 items), public distress (5 items), and work or daily activities (4 items).29, 30 Each domain and the total score are standardized ranging from 0 to 100, and higher scores reflect better weight-related QoL. Positive change scores indicate improvement from baseline for all domains.
Demographic Covariates
Age (continuous), sex (male or female), race (Black or other), and annual family income (<$10,000 per year, $10,000 to $19,999, $20,000 to $39,999, $40,00 to $59,999, $60,000 and above) were self-reported by patients at baseline.
Statistical Analysis
HRQoL changes from baseline were calculated and analyzed using repeated measures linear mixed effects multi-level models, which included random cluster (clinic) effects. In addition to study arm (ILI or UC), clinic, assessment time point, and a study arm-by-time interaction term, the primary analytic model included race, sex, age, and annual family income as covariates. Heterogeneity of treatment effects by sex and race were examined by including three-way (study arm-by-time-by-race or sex) interaction terms in the model. We performed intention-to-treat analyses, which included all patients (regardless of the number of assessments obtained) and used the restricted maximum likelihood method. Estimates are presented as the difference in adjusted least-squares means between the UC and ILI groups with estimate precision represented by the 95% confidence interval.
Analyses for the association between weight loss and HRQoL were conducted only among intervention patients. We used mixed linear regression models to estimate the effect of percent weight change on change in weight- and generic HRQoL. We analyzed change in HRQoL outcomes in the ILI group by categories of weight loss (<5%, 5%–<10%, ≥10%). The random clustering effects of clinics were taken into account. All analyses were conducted with SAS version 9.4 (SAS Institute Inc, Cary, NC) with the significance level set to 0.05 (2-sided).
Results
A total of 803 patients enrolled in the trial (n=451 ILI group); 67% of the sample was Black and 84.4% was female (Table 1). The analytic sample included 786 participants due to missing data for annual family income (n=17). Of the 786 patients with data available for annual family income, 66% (n=515) of the patients had an annual income less than $40,000 per year. The average BMI was 37.2±4.7 kg/m2. Changes in weight-related QoL over two years between the ILI and usual care groups have been previously described (Katzmarzyk, et al. N Engl J Med 2020;383:909–18 Supplementary Appendix Table S8).13 Briefly, changes in total weight-related QoL and four of the five domains (physical function, self-esteem, sexual life, and work) were significantly greater in the ILI group than the UC group at 24 months (mean differences p<0.05). Of the seven generic HRQoL domains and pain intensity, two domains (fatigue, social functioning) showed significant improvements in the ILI group compared to the UC group at 24 months (mean differences p<0.05).
Table 1.
Patient characteristics and patient-reported outcomes at baseline in the PROPEL trial.
| UC | ILI | |||||||
|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||
| Sex | Race | Sex | Race | |||||
|
|
|
|
|
|||||
| Men | Women | Black | Other | Men | Women | Black | Other | |
|
| ||||||||
| N | 71 | 280 | 208 | 143 | 54 | 398 | 332 | 120 |
| Age (y) | 54.4 (12.1) | 49.1 (13.8) | 50.5 (13.3) | 49.7 (14.1) | 53.1 (10.9) | 48.2 (12.8) | 48.8 (12.3) | 48.6 (13.7) |
| Annual Family Income | ||||||||
| <$10,000 | 5 (7.4) | 65 (23.8) | 52 (25.7) | 18 (13.0) | 9 (17.3) | 77 (19.6) | 67 (20.4) | 19 (16.2) |
| $10,000–$19,999 | 7 (10.3) | 66 (24.2) | 46 (22.8) | 27 (19.4) | 6 (11.5) | 89 (22.7) | 70 (21.3) | 25 (21.4) |
| $20,000–$39,999 | 11 (16.2) | 68 (24.9) | 51 (25.3) | 28 (20.1) | 9 (17.3) | 103 (26.2) | 85 (25.9) | 27 (23.1) |
| $40,000–$59,999 | 13 (19.1) | 35 (12.8) | 31 (15.4) | 17 (12.2) | 9 (17.3) | 60 (15.3) | 54 (16.5) | 15 (12.8) |
| ≥$60,000 | 32 (47.1) | 39 (14.3) | 22 (10.9) | 49 (35.3) | 19 (36.5) | 64 (16.3) | 52 (15.9) | 31 (26.5) |
| Missing | 3 | 7 | 6 | 4 | 2 | 5 | 4 | 3 |
| BMI (kg/m2) | 36.8 (4.7) | 37.3 (4.8) | 37.3 (4.8) | 37.1 (4.7) | 37.9 (4.5) | 37.2 (4.6) | 37.1 (4.5) | 37.8 (4.7) |
| IWQOL-L Scores1 | ||||||||
| Total | 80.3 (14.4) | 74.1 (19.0) | 77.4 (18.0) | 72.4 (18.4) | 72.2 (20.5) | 72.9 (19.4) | 75.4 (18.5) | 65.6 (20.6) |
| Physical function | 75.9 (18.1) | 70.2 (21.4) | 71.6 (20.9) | 70.9 (21.0) | 65.7 (22.8) | 68.7 (22.2) | 69.9 (21.7) | 64.3 (23.4) |
| Public distress | 89.9 (14.3) | 86.6 (22.0) | 88.2 (20.8) | 86.0 (20.4) | 82.7 (22.8) | 87.0 (19.6) | 88.9 (17.7) | 80.0 (24.1) |
| Self-esteem | 74.9 (21.7) | 62.4 (28.9) | 70.6 (26.7) | 56.6 (28.0) | 67.0 (27.1) | 61.6 (27.6) | 66.8 (26.2) | 49.5 (27.5) |
| Work/Daily Activities | 89.3 (14.9) | 85.5 (19.5) | 88.0 (16.8) | 83.8 (20.9) | 84.3 (19.0) | 85.9 (19.5) | 88.1 (18.0) | 78.9 (21.6) |
| Sexual Life | 80.7 (27.0) | 78.5 (29.0) | 81.3 (28.2) | 75.6 (28.8) | 74.3 (27.9) | 72.6 (31.5) | 75.0 (30.5) | 66.6 (32.0) |
| PROMIS-29 Scores2 | ||||||||
| Anxiety | 51.6 (8.6) | 52.3 (10.5) | 51.3 (10.2) | 53.4 (9.9) | 50.2 (9.0) | 51.9 (9.7) | 51.1 (9.4) | 53.3 (10.1) |
| Fatigue | 49.7 (8.2) | 51.3 (10.9) | 49.4 (10.8) | 53.1 (9.5) | 50.2 (9.5) | 49.3 (9.9) | 48.2 (9.4) | 52.6 (10.2) |
| Pain Interference | 51.7 (7.0) | 52.6 (10.0) | 52.7 (9.9) | 52.1 (8.8) | 53.2 (9.5) | 51.3 (9.7) | 51.0 (9.6) | 53.0 (9.8) |
| Pain Intensity3 | 2.7 (2.0) | 3.3 (2.8) | 3.3 (2.8) | 2.9 (2.4) | 3.1 (2.6) | 2.9 (2.7) | 2.9 (2.7) | 3.1 (2.7) |
| Physical Functioning | 51.0 (6.7) | 47.4 (8.3) | 47.7 (8.3) | 48.7 (7.8) | 49.2 (8.1) | 48.9 (7.8) | 49.7 (7.7) | 46.8 (7.8) |
| Depression | 47.3 (7.4) | 48.3 (9.0) | 47.1 (8.5) | 49.4 (8.7) | 45.9 (7.5) | 47.1 (8.6) | 46.0 (7.9) | 49.7 (9.3) |
| Sleep Disturbance | 50.5 (7.7) | 51.7 (9.9) | 51.1 (10.4) | 51.9 (8.1) | 51.1 (7.8) | 50.0 (9.4) | 49.7 (9.1) | 51.4 (9.4) |
| Social Functioning | 56.6 (7.5) | 53.7 (9.4) | 54.9 (9.0) | 53.3 (9.2) | 53.5 (9.2) | 55.4 (8.9) | 56.1 (8.5) | 52.8 (9.6) |
Values are mean (SD). UC: Usual care; ILI: intensive lifestyle intervention; IWQOL-L: Impact of Weight on Quality of Life Lite; PROMIS: Patient-Reported Outcomes Measurement Information System.
Transformed scores were calculated for the total and each IWQOL domain so that the score ranges from 0 to 100 with higher scores indicating more of that domain (i.e., a higher score for physical functioning indicates better physical functioning while a higher score for public distress indicates more distress).
Norm-based scores were calculated for each domain on the PROMIS measures, so that a score of 50 represents the mean or average of the reference population. The T-score rescaled the raw score into a standardized T-score with a mean of 50 and a standard deviation (SD) of 10. Therefore, a person with a T-score of 40 is one SD below the mean.
Scale of 0–10 in which higher reflects more pain.
HRQoL Changes by Subgroup
Findings for the differences in mean HRQoL score changes between the UC and ILI groups over two years by sex and race are shown in Table 2 and Table 3, respectively. Both weight-related and generic HRQoL changes were similar for women and men (p for interaction>0.05) with more consistent improvements in weight-related compared to generic HRQoL (Table 2). Over the intervention period, Black patients in the ILI group experienced less improvement in total weight-related QOL compared to patients of other races (p for interaction=0.02, Figure 1). The mean differences from baseline between the UC and ILI groups for total weight-related QoL at 6, 12, and 24 months were 7.6 (95% CI: 5.0, 10.2), 7.5 (95% CI: 4.9, 10.2), and 6.6 (95% CI: 3.9, 9.4) among Black patients and 8.0 (95% CI: 4.6, 11.4), 9.9 (95% CI: 6.1, 13.7), and 8.3 (95% CI: 4.1, 12.4) among patients of other races. Changes for individual domains of weight-related QoL did not significantly differ by race (p for interaction>0.05, Table 3). There were no differences by race for any generic HRQoL domain (p for interaction>0.05).
Table 2.
Differences between usual care and the intensive lifestyle group for changes in mean quality of life scores over two years in women and men.
| Variable | Women | Men | Interaction |
|---|---|---|---|
|
| |||
| Change in IWQOL-L Total Score1 | p = 0.96 | ||
| At 6 months | 7.93 (5.59, 10.27) | 7.72 (3.74,11.71) | |
| At 12 months | 8.11 (5.66, 10.57) | 7.99 (3.77, 12.21) | |
| At 24 months | 7.13 (4.55, 9.71) | 6.45 (1.72, 11.17) | |
| Change in IWQOL-L Physical Function1 | p = 0.36 | ||
| At 6 months | 11.28 (7.88, 14.67) | 11.03 (4.98, 17.09) | |
| At 12 months | 10.99 (7.54, 14.44) | 12.31 (6.52, 18.10) | |
| At 24 months | 8.72 (5.25, 12.19) | 7.98 (0.08, 15.87) | |
| Change in IWQOL-L Public Distress1 | p = 0.60 | ||
| At 6 months | 2.07 (−1.32, 5.45) | 5.01 (−1.11, 11.14) | |
| At 12 months | 3.60 (0.07, 7.14) | 6.00 (1.77, 10.23) | |
| At 24 months | 3.49 (−0.10, 7.09) | 2.93 (−1.51, 7.36) | |
| Change in IWQOL-L Self Esteem1 | p = 0.80 | ||
| At 6 months | 7.72 (4.26, 11.19) | 8.67 (1.99, 15.35) | |
| At 12 months | 8.71 (5.02, 12.40) | 6.92 (−0.79, 14.62) | |
| At 24 months | 7.05 (3.19, 10.91) | 6.95 (−0.97, 14.88) | |
| Change in IWQOL-L Sexual Life1 | p = 0.64 | ||
| At 6 months | 11.60 (7.10, 16.11) | 2.85 (−6.17, 11.87) | |
| At 12 months | 10.00 (5.53, 14.46) | 7.58 (−2.56, 17.71) | |
| At 24 months | 11.52 (6.68, 16.36) | −0.07 (−10.35, 10.20) | |
| Change in IWQOL-L Work/Daily Activity1 | p = 0.55 | ||
| At 6 months | 2.83 (−0.01, 5.66) | 2.57 (−2.66, 7.80) | |
| At 12 months | 3.96 (1.01, 6.91) | 3.80 (−1.96, 9.57) | |
| At 24 months | 3.87 (0.71, 7.03) | 6.45 (1.13, 11.77) | |
| Change in PROMIS Anxiety2 | p = 0.56 | ||
| At 6 months | −2.17 (−3.99, −0.34) | −0.50 (−3.69, 2.69) | |
| At 12 months | −0.69 (−2.44, 1.07) | −0.65 (−4.09, 2.79) | |
| At 24 months | −0.53 (−2.44, 1.39) | −0.01 (−3.59, 3.57) | |
| Change in PROMIS Fatigue2 | p = 0.77 | ||
| At 6 months | −2.22 (−3.98, −0.47) | −3.90 (−7.22, −0.57) | |
| At 12 months | −1.04 (−2.89, 0.81) | −3.14 (−6.45, 0.18) | |
| At 24 months | −1.57 (−3.47, 0.32) | −2.96 (−6.62, 0.70) | |
| Change in PROMIS Pain Interference2 | p = 0.22 | ||
| At 6 months | −1.08 (−2.49, 0.33) | −3.92 (−6.84, −1.00) | |
| At 12 months | −0.96 (−2.48, 0.56) | −2.46 (−5.77, 0.86) | |
| At 24 months | −1.21 (−2.84, 0.43) | −1.02 (−4.48, 2.44) | |
| Change in PROMIS Pain Intensity2 | p = 0.55 | ||
| At 6 months | 0.20 (−0.60, 0.20) | −0.69 (−1.79, 0.40) | |
| At 12 months | −0.06 (−0.52, 0.39) | −0.18 (−1.30, 0.94) | |
| At 24 months | −0.25 (−0.70, 0.20) | 0.02 (−1.21, 1.25) | |
| Change in PROMIS Physical Function1 | p = 0.54 | ||
| At 6 months | 2.32 (1.21, 3.43) | 1.98 (−2.18, 6.14) | |
| At 12 months | 1.78 (0.63, 2.94) | 1.42 (−2.78, 5.63) | |
| At 24 months | 1.36 (0.15, 2.58) | 1.15 (−3.18, 5.48) | |
| Change in PROMIS Depression2 | p = 0.94 | ||
| At 6 months | −0.79 (−2.10, 0.52) | −0.35 (−2.79, 2.09) | |
| At 12 months | −0.74 (−2.07, 0.59) | 1.18 (−1.60, 3.96) | |
| At 24 months | −1.07 (−2.49, 0.36) | 0.40 (−2.23, 3.02) | |
| Change in PROMIS Sleep Disturbance2 | p = 0.20 | ||
| At 6 months | −2.31 (−3.76, −0.85) | −2.78 (−5.91, 0.34) | |
| At 12 months | −1.10 (−2.70, 0.50) | −1.21 (−4.51, 2.09) | |
| At 24 months | −1.16 (−2.78, 0.46) | −0.69 (−3.81, 2.44) | |
| Change in PROMIS Social Functioning1 | p = 0.67 | ||
| At 6 months | 1.73 (0.46, 3.00) | 3.35 (−0.44, 7.15) | |
| At 12 months | 1.14 (−0.23, 2.50) | 2.56 (−1.57, 6.70) | |
| At 24 months | 1.02 (−0.37, 2.41) | 3.21 (−1.05, 7.46) | |
IWQOL-L: Impact of Weight on Quality of Life Lite; PROMIS: Patient-Reported Outcomes Measurement Information System. Analyzed using multi-level mixed effects linear regression. All models included race, age, and annual family income as covariates.
Higher change scores indicate greater improvement from baseline.
Lower scores indicate greater improvement from baseline.
Table 3.
Differences between usual care and the intensive lifestyle group for changes in mean quality of life scores over two years in Black and Other race participants.
| Variable | Black | Other | Interaction |
|---|---|---|---|
|
| |||
| Change in IWQOL-L Total Score1 | p = 0.02 | ||
| At 6 months | 7.57 (4.99, 10.16) | 7.99 (4.56, 11.41) | |
| At 12 months | 7.53 (4.89, 10.16) | 9.94 (6.14, 13.74) | |
| At 24 months | 6.64 (3.87, 9.40) | 8.28 (4.12, 12.43) | |
| Change in IWQOL-L Physical Function1 | p = 0.08 | ||
| At 6 months | 12.11 (8.40, 15.83) | 8.64 (2.94, 14.33) | |
| At 12 months | 11.20 (7.57, 14.83) | 10.96 (4.83, 17.09) | |
| At 24 months | 9.11 (5.46, 12.75) | 7.76 (1.10, 14.41) | |
| Change in IWQOL-L Public Distress1 | p = 0.33 | ||
| At 6 months | 1.81 (−1.42, 5.04) | 4.02 (−1.20, 9.23) | |
| At 12 months | 2.61 (−0.73, 5.940 | 7.14 (1.98, 12.30) | |
| At 24 months | 2.03 (−1.33, 5.39) | 5.52 (0.09, 10.95) | |
| Change in IWQOL-L Self Esteem1 | p = 0.23 | ||
| At 6 months | 6.73 (3.18, 10.28) | 10.01 (4.90, 15.12) | |
| At 12 months | 8.28 (4.47, 12.09) | 9.84 (4.28, 15.39) | |
| At 24 months | 6.08 (2.04, 10.11) | 10.46 (4.58, 16.33) | |
| Change in IWQOL-L Sexual Life1 | p = 0.15 | ||
| At 6 months | 9.88 (4.99, 14.77) | 9.98 (3.55, 16.41) | |
| At 12 months | 7.57 (2.83, 12.31) | 13.17 (6.18, 20.17) | |
| At 24 months | 9.27 (4.09, 14.44) | 11.87 (4.36, 19.38) | |
| Change in IWQOL-L Work/Daily Activity1 | p = 0.42 | ||
| At 6 months | 2.77 (−0.63, 6.18) | 3.33 (−1.94, 8.60) | |
| At 12 months | 3.71 (0.13, 7.29) | 5.82 (0.53, 11.11) | |
| At 24 months | 3.89 (0.22, 7.56) | 5.54 (−0.21, 11.28) | |
| Change in PROMIS Anxiety2 | p = 0.31 | ||
| At 6 months | −1.78 (−3.80, 0.23) | −2.26 (−4.95, 0.44) | |
| At 12 months | −1.15 (−3.13, 0.83) | 0.004 (−2.52, 2.53) | |
| At 24 months | −1.04 (−3.15, 1.08) | 0.35 (−2.52, 3.22) | |
| Change in PROMIS Fatigue2 | p = 0.47 | ||
| At 6 months | −2.68 (−4.78, −0.57) | −2.30 (−4.86, 0.26) | |
| At 12 months | −1.48 (−3.68, 0.72) | −0.97 (−3.64, 1.70) | |
| At 24 months | −1.47 (−3.75, 0.81) | −2.73 (−5.49, 0.03) | |
| Change in PROMIS Pain Interference2 | p = 0.39 | ||
| At 6 months | −2.11 (−3.70, −0.53) | −0.25 (−2.39, 1.89) | |
| At 12 months | −0.90 (−2.58, 0.78) | −2.03 (−4.48, 0.42) | |
| At 24 months | −1.12 (−2.93, 0.69) | −1.35 (−3.94, 1.23) | |
| Change in PROMIS Pain Intensity2 | p = 0.74 | ||
| At 6 months | −0.36 (−0.86, 0.13) | −0.03 (−0.60, 0.54) | |
| At 12 months | 0.02 (−0.52, 0.56) | −0.18 (−0.84, 0.47) | |
| At 24 months | −0.20 (−0.74, 0.34) | −0.28 (−0.97, 0.40) | |
| Change in PROMIS Physical Function1 | p = 0.76 | ||
| At 6 months | 2.22 (0.90, 3.54) | 2.21 (0.06, 4.37) | |
| At 12 months | 1.78 (0.40, 3.16) | 1.50 (−0.66, 3.66) | |
| At 24 months | 1.54 (0.14, 2.94) | 0.81 (−1.50, 3.13) | |
| Change in PROMIS Depression2 | p = 0.97 | ||
| At 6 months | −0.73 (−2.07, 0.60) | −0.64 (−3.05, 1.77) | |
| At 12 months | −0.54 (−1.97, 0.88) | −0.30 (−2.66, 2.05) | |
| At 24 months | −0.77 (−2.24, 0.71) | −1.31 (−3.88, 1.25) | |
| Change in PROMIS Sleep Disturbance2 | p = 0.43 | ||
| At 6 months | −2.24 (−3.92, −0.56) | −2.98 (−5.32, −0.64) | |
| At 12 months | −0.95 (−2.75, 0.85) | −1.54 (−4.16, 1.08) | |
| At 24 months | −1.11 (−2.92, 0.70) | −0.96 (−3.57, 1.66) | |
| Change in PROMIS Social Functioning1 | p = 0.93 | ||
| At 6 months | 1.78 (−0.00, 3.56) | 2.10 (0.14, 4.05) | |
| At 12 months | 1.44 (−0.43, 3.31) | 1.09 (−1.08, 3.25) | |
| At 24 months | 1.50 (−0.38, 3.39) | 0.68 (−1.57, 2.94) | |
IWQOL-L: Impact of Weight on Quality of Life Lite; PROMIS: Patient-Reported Outcomes Measurement Information System. Analyzed using multi-level mixed effects linear regression. All models included sex, age, and annual family income as covariates.
Higher change scores indicate greater improvement from baseline.
Lower scores indicate greater improvement from baseline.
Figure 1.
Change in weight-related quality of life from baseline according to race (Panel A) and sex (Panel B). ILI denotes the Intensive Lifestyle Intervention condition while UC represents Usual Care. Markers indicate estimated means and error bars represent standard errors.
HRQoL Changes and Weight Loss
Among intervention patients, 386 had data available for body weight and one or more of the QoL variables at baseline and at least one other time point. Among included patients, 53.6% lost less than 5% of their initial body weight, 25.4% achieved between 5 and 10% weight loss, and 21.0% achieved at least 10% weight loss at 24 months. Mean HRQoL score changes by weight loss category are shown in Table 4. Changes in total weight-related QoL across weight loss categories between baseline and 24 months were 6.3 (95% CI: 4.1, 8.6) for those with <5% weight loss, 10.6 (95% CI: 8.1, 13.1) for those with 5-<10% weight loss, and 16.0 (95% CI: 13.6, 18.4) for those with ≥10% weight loss (p for trend<0.001). Greater weight loss was significantly associated with greater improvements in most individual weight-related QoL domains at all time points; p for trend did not reach significance for only public distress at 6 and 12 months, and work/daily activity at 12 months. Similar results were found for generic HRQoL in that greater weight loss was related to greater improvements in patient’s pain intensity rating and five of the seven generic HRQoL domains at all follow-up timepoints (p for trend<0.05). As an example, changes in the generic HRQoL domain social functioning across weight loss categories between baseline and 24 months were −0.1 (95% CI: −1.3, 1.0) for <5% weight loss, 2.5 (95% CI: 0.8, 4.1) for 5-<10% weight loss, and 4.2 (95% CI: 2.4, 6.1) for ≥10% weight loss (p for trend <0.05). Greater weight loss was not consistently associated with the anxiety and depression generic HRQoL domains across the follow-up timepoints.
Table 4.
Change in quality of life scores in the ILI group over two years, by categories of weight loss.
| <5% Weight loss | 5%–<10% Weight loss | ≥10% Weight loss | p for trend | |
|---|---|---|---|---|
|
| ||||
| IWQOL-L Total Score1 | ||||
| At 6 months | 6.3 (4.1, 8.6) | 10.6 (8.1, 13.1) | 16.0 (13.6, 18.4) | <0.001 |
| At 12 months | 7.8 (5.4, 10.3) | 12.3 (9.6, 15.0) | 17.8 (15.0, 20.5) | <0.001 |
| At 24 months | 7.6 (5.1, 10.0) | 15.1 (11.8, 18.5) | 19.1 (15.5, 22.7) | <0.001 |
| IWQOL-L Physical Function1 | ||||
| At 6 months | 8.4 (5.1, 11.7) | 12.7 (9.2, 16.3) | 19.0 (15.5, 22.4) | <0.001 |
| At 12 months | 8.2 (5.1, 11.3) | 15.4 (11.9, 18.9) | 20.0 (16.5, 23.5) | <0.001 |
| At 24 months | 6.3 (3.6, 9.1) | 17.1 (13.1, 21.0) | 22.7 (18.5, 27.0) | <0.001 |
| IWQOL-L Public Distress1 | ||||
| At 6 months | 3.1 (0.5, 5.8) | 4.6 (1.6, 7.5) | 7.5 (4.7, 10.4) | 0.080 |
| At 12 months | 4.5 (1.5, 7.6) | 7.9 (4.6, 11.3) | 8.7 (5.3, 12.0) | 0.094 |
| At 24 months | 3.7 (0.7, 6.6) | 10.3 (6.3, 14.2) | 8.1 (3.9, 12.2) | 0.006 |
| IWQOL-L Self Esteem1 | ||||
| At 6 months | 6.6 (3.4, 9.9) | 12.5 (8.9, 16.1) | 22.1 (18.7, 25.6) | <0.001 |
| At 12 months | 11.2 (7.8, 14.6) | 13.1 (9.2, 17.0) | 25.2 (21.4, 29.1) | <0.001 |
| At 24 months | 12.3 (9.1, 15.4) | 17.3 (12.7, 21.9) | 25.6 (20.6, 30.6) | <0.001 |
| IWQOL-L Sexual Life1 | ||||
| At 6 months | 7.3 (2.9, 11.8) | 13.3 (8.4, 18.3) | 16.3 (11.6, 21.0) | 0.023 |
| At 12 months | 9.2 (4.9, 13.4) | 12.0 (7.2, 16.7) | 18.7 (14.0, 23.4) | 0.012 |
| At 24 months | 11.6 (7.6, 15.7) | 17.8 (12.0, 23.7) | 20.6 (14.2, 27.0) | 0.038 |
| IWQOL-L Work/Daily Activity1 | ||||
| At 6 months | 4.2 (1.8, 6.6) | 4.6 (1.9, 7.2) | 8.7 (6.2, 11.3) | 0.021 |
| At 12 months | 4.3 (1.2, 7.4) | 7.8 (4.4, 11.3) | 8.8 (5.4, 12.3) | 0.064 |
| At 24 months | 3.9 (1.1, 6.7) | 8.7 (4.7, 12.6) | 10.0 (5.8, 14.2) | 0.019 |
| PROMIS Anxiety2 | ||||
| At 6 months | −1.1 (−3.2, 1.1) | −1.7 (−4.0, 0.6) | −3.2 (−5.5, −0.9) | 0.176 |
| At 12 months | −0.1 (−1.9, 1.7) | −0.7 (−2.6, 1.3) | −2.9 (−4.8, −0.9) | 0.040 |
| At 24 months | −0.8 (−2.4, 0.7) | −1.3 (−3.4, 0.9) | −2.0 (−4.3, 0.3) | 0.682 |
| PROMIS Fatigue2 | ||||
| At 6 months | −1.0 (−2.7, 0.7) | −2.6 (−4.4, −0.8) | −5.9 (−7.7, −4.1) | <0.001 |
| At 12 months | 0.7 (−0.9, 2.3) | −3.2 (−5.0, −1.4) | −5.1 (−6.9, −3.3) | <0.001 |
| At 24 months | −0.5 (−2.1, 1.1) | −3.0 (−5.2, −0.8) | −6.2 (−8.6, −3.8) | <0.001 |
| PROMIS Pain Interference2 | ||||
| At 6 months | 0.2 (−1.1, 1.6) | −1.2 (−2.7, 0.3) | −3.2 (−4.6, −1.8) | 0.003 |
| At 12 months | 1.6 (0.1, 3.1) | −2.0 (−3.7, −0.3) | −3.1 (−4.8, −1.4) | <0.001 |
| At 24 months | 0.4 (−1.0, 1.7) | −1.0 (−3.0, 0.9) | −4.1 (−6.2, −1.9) | 0.003 |
| PROMIS Pain Intensity2 | ||||
| At 6 months | −0.1 (−0.5, 0.3) | 0.1 (−0.3, 0.5) | −0.7 (1.1, −0.3) | 0.011 |
| At 12 months | 0.9 (0.4, 1.3) | −0.6 (−1.1, −0.1) | −0.6 (−1.1, −0.1) | <0.001 |
| At 24 months | 0.4 (0.01, 0.8) | −0.3 (−0.8, 0.3) | −0.7 (−1.3, −0.1) | 0.006 |
| PROMIS Physical Function1 | ||||
| At 6 months | 1.1 (−0.1, 2.2) | 2.6 (1.3, 3.8) | 3.2 (2.0, 4.4) | 0.018 |
| At 12 months | 0.5 (−0.7, 1.6) | 2.2 (0.9, 3.5) | 2.7 (1.5, 4.0) | 0.023 |
| At 24 months | −0.2 (−1.2, 0.8) | 2.2 (0.8, 3.6) | 3.6 (2.0, 5.1) | <0.001 |
| PROMIS Depression2 | ||||
| At 6 months | 0.4 (−0.8, 1.6) | 0.3 (−1.0, 1.7) | −1.0 (−2.2, 0.3) | 0.235 |
| At 12 months | 1.1 (−0.2, 2.4) | 0.2 (−1.2, 1.7) | −1.2 (−2.6, 0.3) | 0.063 |
| At 24 months | 0.9 (−0.3, 2.1) | −0.7 (−2.4, 1.0) | −2.0 (−3.8, −0.1) | 0.03 |
| PROMIS Sleep Disturbance2 | ||||
| At 6 months | −0.7 (−2.0, 0.7) | −1.7 (−3.1, −0.2) | −3.2 (−4.6, −1.7) | 0.042 |
| At 12 months | 1.3 (−0.2, 2.7) | −1.8 (−3.4, −0.1) | −2.5 (−4.1, −0.9) | 0.001 |
| At 24 months | −0.01 (−1.3, 1.3) | −3.3 (−5.2, −1.5) | −1.6 (−3.6, 0.4) | 0.014 |
| PROMIS Social Functioning1 | ||||
| At 6 months | 0.8 (−0.4, 2.1) | 1.8 (0.4, 3.1) | 3.6 (2.3, 5.0) | 0.011 |
| At 12 months | −0.8 (−2.1, 0.6) | 2.8 (1.3, 4.3) | 4.6 (3.1, 6.1) | <0.001 |
| At 24 months | −0.1 (−1.3, 1.0) | 2.5 (0.8, 4.1) | 4.2 (2.4, 6.1) | <0.001 |
IWQOL-L: Impact of Weight on Quality of Life Lite; PROMIS: Patient-Reported Outcomes Measurement Information System. Analyzed using multi-level mixed effects linear regression. All models included race, age, and annual family income as covariates.
Higher change scores indicate greater improvement from baseline.
Lower scores indicate greater improvement from baseline.
Discussion
In the PROPEL intervention, greater weight loss was associated with greater HRQoL improvements over 24 months in a low-income primary care population, reflecting the importance of weight loss for better QoL.13 While differences in mean weight loss from baseline between the UC and ILI were slightly attenuated at 24 months compared to six months,13 weight-related QoL improvements were maintained across the two-year intervention period suggesting that weight-related QoL improvements following weight loss may be long-lasting. Our findings are concordant with others finding improvements in QoL in response to a weight loss intervention.2, 28, 31, 32 These studies report improvements in weight-related QoL which were maintained at 24 months31 and significant improvements in self-reported general health with greater percent weight loss was associated with greater improvements.32
While there is not a universally agreed upon definition of a clinically significant difference in HRQoL, the minimal clinically important difference (MCID) reflects the smallest change in an outcome which patients perceive as beneficial.33 The MCID for the PROMIS-29 instrument has not yet been determined for patients with obesity, so we are unable to assert whether our findings represent clinically significant improvements for generic HRQoL. The IWQOL-Lite total weight-related QOL score MCID was reported as between 7.7 and 12.0 in a cohort of patients with severe obesity.34 Within the present study, the total weight-related QoL change for intervention patients who lost at least 5% of their initial body weight at 24 months of follow-up exceeds the aforementioned MCID point estimate range. Thus, embedding a health coach on a primary care team to deliver a lifestyle-based weight loss treatment can yield significant and persistent improvements in weight-related QoL.
Studies have shown heterogeneity of treatment effects in response to clinical trials for weight loss. For example, a previous study from the PROPEL trial reported that Black patients lost significantly less weight than patients of other races, and that daily weighing and session attendance mediated a significant portion of the race differences.35 However, less is known about subgroup differences for HRQoL changes associated with weight loss. In the present study, men and women in the ILI experienced similar changes in HRQoL (i.e., no interaction by sex for either type of QoL) with overall improvements in weight-related QoL relative to UC and mixed results for generic HRQoL. While women with obesity may experience poorer HRQoL compared to men,2, 36 the limited number of studies examining sex differences in HRQoL response to weight loss lean toward there being no differences between men and women.8, 28, 37–39 Race differences in weight-related QoL, but not generic HRQoL, were identified in which Black patients experienced smaller improvements compared to patients of other races. Considering the attention recently directed at race-related disparities in health care,40 these racial differences found in PROPEL are noteworthy. Prior studies have shown differences by race in weight-related and generic HRQoL among individuals with obesity with black individuals having higher HRQoL compared to those of other races.41–43 However, few studies have explored race differences in HRQoL changes following weight loss. Future studies should be designed to test for the heterogeneity of treatment effects in the HRQoL response to weight loss by race and sex to better understand the relationship and factors (e.g., environmental, psychological, intervention characteristics, cultural, etc.) that may mediate identified differences. Understanding the causes underlying differential response to weight loss programs will allow researchers and public health practitioners to better tailor future weight loss programs’ design, delivery format, and behavior change strategies to individuals using a precision medicine approach.
The overall lack of subgroup differences for generic HRQoL may be due to lower sensitivity to change of the PROMIS-29 in a weight loss trial. Indeed, generic HRQoL instruments, such as the PROMIS-29, are designed to deliver information that is widely applicable to the general population whereas the IWQOL-L is a disease-specific instrument designed to assess HRQoL domains most relevant to individuals with obesity, like those in the PROPEL study.28 Disease-specific HRQoL instruments also tend to be more sensitive to change during interventions that target those conditions.28 These findings underscore the importance of using instruments tailored to the health concerns of the study population.
In our study, greater weight loss was associated with greater weight-related and generic HRQoL with the greatest improvements experienced by those who lost at least 10% of their initial body weight. A recent “review of reviews” inclusive of 12 meta-analyses and systematic reviews2 found improvements in weight-related and generic health-related QoL following bariatric surgery and evidence, though less consistent and pronounced, of improved QoL following non-surgical weight loss. The authors postulated that the consistent improvements in QoL with bariatric surgery may be due to greater weight loss following that type of treatment compared to lifestyle change or obesity treatment medication.2 This is further corroborated by a study among adults with obesity in a weight management program inclusive of dietary counseling and medication which found that the largest improvements in total weight-related QOL were observed for those who lost at least 20% of their initial body weight followed by 15%−19.9%, 10–14.9%, and less than 10% weight loss in a relatively linear manner.28 Thus, in our study and others, greater QoL improvements were associated with greater percent weight loss. Future studies using randomized designs should examine the amount of weight loss needed for HRQoL improvements.
This study makes a novel contribution to the literature by including measures of both generic HRQoL, widely applicable to most patients, and weight-related QOL, which focuses on aspects of HRQoL important to patients with obesity. A major strength of this study is the investigation of heterogeneity of treatment effects by sex and race to better understand the complexities of the relationship between weight loss and changes in HRQoL. The study findings may also be generalizable to people, particularly women, with obesity in Louisiana given that the study population included patients with varied racial, income, and educational backgrounds living in both urban and rural areas across the state (4 of 18 clinics were located in rural areas, representing 9% of enrolled patients)44. Finally, while this study is limited in its ability to make causal inferences since the PROPEL study was not designed to examine the association between changes in HRQoL and changes in body weight, the findings point to a significant relationship between weight loss and HRQoL improvement and the need for future research designed to elucidate the causal mechanism.
Findings for men should be interpreted carefully since the study sample was predominantly female (84%), although this is similar to other studies on this topic, where women comprised 72% of the sample in a study of BMI and HRQoL.8 Further research should seek to optimize recruitment methods to increase male participation in weight management trials. The sample was also comprised of existing patients of primary care clinics who may be more activated to health improvement, and although 75% of American adults have a primary care provider,45 future studies are needed to understand if similar relationships exist among individuals who are not health care users. Additionally, missing data may have biased the findings; for example, we may have overestimated the actual improvement in HRQoL associated with the intervention and weight loss if patients in the ILI group with poor HRQoL were systematically less likely to complete their follow-up study visits. The last consideration is that the instruments we used may not have measured all elements of HRQoL that are important to patients with obesity necessitating future research.
In conclusion, heterogeneity of weight-related QoL response by race was identified in the PROPEL intervention, and greater percent reductions in body weight across the intervention period were associated with greater improvements in weight- and generic HRQoL. These findings highlight the importance of considering patient-reported outcomes tailored to the study population and the differential impact of personal characteristics on clinical trial treatment response. As interest in including patient-reported outcomes in clinical trials grows, differential treatment response within such metrics is a worthwhile consideration to promote more equitable improvement.
Study Importance.
What is already known?
Health-related quality of life (HRQoL) is negatively associated with body mass index, obesity, other chronic diseases, and the risk of premature mortality.
Little is known about how HRQoL changes in response to weight loss and the potential for heterogeneity of treatment effects, especially among patients enrolled in a lifestyle intervention. The few studies on this topic have largely been performed in the context of bariatric surgery or obesity medications.
HRQoL can be assessed by instruments which measure generic (non-disease specific) HRQoL or obesity-specific QoL, and relationships may differ between these two types of assessments.
What does this study add?
This study found that a pragmatic, lifestyle-based weight loss intervention delivered within primary care to a predominantly low-income population can yield significant and long-term improvements in weight-related QoL.
Subgroup analyses revealed that Black patients experienced smaller improvements in weight-related QoL, but not generic HRQoL, compared to patients of other races, which represents a novel contribution to the literature.
The findings corroborate those from other studies that greater QoL improvements are associated with greater weight loss.
How might these results change the direction of research?
Future research should tailor the patient-reported outcomes to the study population by including disease-specific measurement tools when available and examine factors influencing the differential impact of patient sociodemographic characteristics on clinical treatment response to promote more equitable improvement.
Acknowledgements
We thank the patients, assessment technicians, health coaches, members of the patient advisory boards, community monitoring board, and the project management committee, and the data and safety monitoring board without whom this project would not have been possible. In‐kind support for PROPEL was provided by Nutrisystem and Health and Nutrition Technology. The statements in this article do not necessarily represent the views of PCORI or its board of governors or methodology committee and are solely the responsibility of the authors. The de-identified patient dataset is available upon reasonable request to the Principal Investigator: Peter.Katzmarzyk@pbrc.edu. A data use agreement with Pennington Biomedical Research Center is required. The protocol, statistical analysis plan, and a full list of the PROPEL Research Group were previously published.13
Funding:
Supported by an award (OB-1402–10977) from PCORI, by a grant (U54GM104940) from the National Institute of General Medical Sciences of the National Institutes of Health, which funds the Louisiana Clinical and Translational Science Center, and by a grant (P30DK072476) from the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, which funds the Pennington/Louisiana Nutrition Obesity Research Center. In-kind support to PROPEL include Health and Nutrition Technology and Nutrisystem.
Footnotes
Disclosures: CJL serves on a DSMB for NovoNordisk for the DEFINE 3 Trial on CagriSemi. PK, RN, JA, TD, EM, KD, EPH, CA, and CM report NIH grants to their institution. PK reports research contracts between WW International and his institution. CM reports research grants between Lilly and his institution. JA reports research grants between USDA, NSF, FFAR and the HASS Avocado Board and his institution. JA reports a speaking honorarium from University of Missouri, conference attendance support from The Obesity Society, and serves on the LA-CEAL Advisory Board. CM reports royalties from ABGIL, consulting fees from Wondr Health, EHE Health, and the Commission on Dietetic Registration. EPH serves on the PCORI Board of Governors; this research was conducted before Dr. Price‐Haywood was appointed. All other authors report no conflicts of interest.
Clinical Trial Registration: NCT02561221
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