Effect of Financial Incentives and Environmental Strategies on Weight Loss in the Healthy Weigh Study: A Randomized Clinical Trial

Abstract

Importance: Modest weight loss can lead to meaningful risk reduction in adults with obesity. Although both behavioral economic incentives and environmental change strategies have shown promise for initial weight loss, to date they have not been combined, or compared, in a randomized clinical trial.

Objective: To test the relative effectiveness of financial incentives and environmental strategies, alone and in combination, on initial weight loss and maintenance of weight loss in adults with obesity.

Design, setting, and participants: This randomized clinical trial was conducted from 2015 to 2019 at 3 large employers in Philadelphia, Pennsylvania. A 2-by-2 factorial design was used to compare the effects of lottery-based financial incentives, environmental strategies, and their combination vs usual care on weight loss and maintenance. Interventions were delivered via website, text messages, and social media. Participants included adult employees with a body mass index (BMI; weight in kilograms divided by height in meters squared) of 30 to 55 and at least 1 other cardiovascular risk factor. Data analysis was performed from June to July 2021.

Interventions: Interventions included lottery-based financial incentives based on meeting weight loss goals, environmental change strategies tailored for individuals and delivered by text messages and social media, and combined incentives and environmental strategies.

Main outcome and measures: The primary outcome was weight change from baseline to 18 months, measured in person.

Results: A total of 344 participants were enrolled, with 86 participants each randomized to the financial incentives group, environmental strategies group, combined financial incentives and environmental strategies group, and usual care (control) group. Participants had a mean (SD) age of 45.6 (10.5) years and a mean (SD) BMI of 36.5 (7.1); 247 participants (71.8%) were women, 172 (50.0%) were Black, and 138 (40.1%) were White. At the primary end point of 18 months, participants in the incentives group lost a mean of 5.4 lb (95% CI, -11.3 to 0.5 lb [mean, 2.45 kg; 95% CI, -5.09 to 0.23 kg]), those in the environmental strategies group lost a mean of a 2.2 lb (95% CI, -7.7 to 3.3 lb [mean, 1.00 kg; 95% CI, -3.47 to 1.49 kg]), and the combination group lost a mean of 2.4 lb (95% CI, -8.2 to 3.3 lb [mean, 1.09 kg; 95% CI, -3.69 to 1.49 kg]) more than participants in the usual care group. Financial incentives, environmental change strategies, and their combination were not significantly more effective than usual care. At 24 months, after 6 months without an intervention, the difference in the change from baseline was similar to the 18-month results, with no significant differences among groups.

Conclusions and relevance: In this randomized clinical trial, across all study groups, participants lost a modest amount of weight but those who received financial incentives, environmental change, or the combined intervention did not lose significantly more weight than those in the usual care group. Employees with obesity may benefit from more intensive individualized weight loss strategies.

Trial registration: ClinicalTrials.gov Identifier: NCT02878343.

Figure 1.. Healthy Weigh CONSORT Flow Diagram

BMI indicates body mass index. ^aThese are the top 4 reasons for exclusion. Participants may have multiple reasons for ineligibility.

Figure 2.. Interaction Analyses for Incentive Groups vs Nonincentive Groups and for Environmental Strategies Groups vs Non–Environmental Strategies Groups

The interaction regression models are adjusted by the randomization strata variables of sex, employer, initial body mass index (BMI; calculated as weight in kilograms divided by height in meters squared); study group; and baseline participant characteristics of age, race/ethnicity, annual household income, education, baseline weight, marital status, household size, and stage of change. The main outcome shown in panel A is the difference of least square mean between incentive groups (incentive group plus combined group) and nonincentive groups (environmental strategies group plus usual care group). The main outcome shown in panel B is the difference of least square mean between environmental strategies groups (environmental strategies group plus combined group) and non–environmental strategies groups (incentive group plus usual care group). ^aFor annual household income, data are missing for 31 participants. For the intention-to-treat analysis, we preformed multiple imputation to the missing cases. The number of participants presented here is from the first iteration of multiple imputation.

Figure 3.. Days per Week Self-weighing Was Performed Among Study Participants Who Successfully Set Up the Scales

Participants who did not have scales are excluded in the analysis, and those who withdrew are excluded from the denominator from the week they withdrew. Participants in usual care group are not included here because they did not have scales. The first week data are not included because it was a grace period for setting up the scale. The line of week 75 shows the wash-out period: 244 participants successfully set up their scales, including 79 in the incentive group, 82 in the environmental strategies (ES) group, and 83 in the combined group. At week 73, denominators were 73, 80, and 78 for the incentive, ES, and combined groups, respectively.