Effect of Financial Incentives and Environmental Strategies on Weight Loss in the Healthy Weigh Study

Key Points Question What is the relative effectiveness of financial incentives and environmental change strategies, alone and in combination, on initial weight loss and maintenance of weight loss in employees with obesity? Findings In this randomized clinical trial, at the 18-month primary end point, participants in the incentives group lost a mean of 5.4 lb (2.45 kg), those in the environmental strategies group lost a mean of 2.2 lb (1.00 kg), and the combination group lost a mean of 2.4 lb (1.09 kg) more than the usual care group. None of the strategies was significantly more effective than usual care. Meaning Across all study groups, participants lost a modest amount of weight but those who received interventions did not lose significantly more weight, suggesting that more intensive individualized weight loss strategies may be needed.


Introduction
The prevalence of obesity has increased significantly in the US in recent decades. Between 1960 and 2014, the prevalence of obesity-defined as a body mass index (BMI; weight in kilograms divided by height in meters squared) of more than 30-among US adults increased from 11.0% to 35.0% among men and from 16.0% to 40.4% among women. 1 Obesity in adulthood is associated with higher rates of cardiovascular risk factors, disability, hospitalization, health care expenditures, and mortality risk. [2][3][4] A modest amount of weight loss, approximately 10 lb (4.5 kg), can reduce the incidence of diabetes and improve risk factors such as hypertension and hyperglycemia. 5,6 A number of approaches are successful in achieving initial weight loss, 7 but maintaining weight loss is challenging. 8,9 Although both behavioral economic and environmental strategies have shown promise, to date they have not been combined, or compared, in a randomized clinical trial. Financial incentives have been shown to modify health behaviors, [10][11][12][13][14] including inducing initial weight loss. [12][13][14][15] Environmental change strategies, such as providing easily accessible healthful foods and building exercise opportunities into workplace design, have been proposed as critical to solving the population-wide problem of obesity 16 and have been shown to affect food intake and physical activity. 16-21 Some environmental intervention strategies in workplaces have helped to increase physical activity and promote weight control. 21 However, their effectiveness has not been tested in the context of longterm weight loss or weight maintenance or when combined with financial incentives. Furthermore, the comparative effectiveness of incentive and environmental strategies is not known. 22 We, therefore, undertook the present study to answer the following question: How effective are financial incentives and environmental strategies, alone and in combination, on initial weight loss and maintenance of weight loss (primary outcome at 18 months; secondary outcome at 24 months) in employed adults with obesity?

Overview of Study Design
The Healthy Weigh Study is a randomized clinical trial evaluating the comparative effectiveness of lottery-based incentive and environmental strategies, alone or in combination, to a control intervention in a population of urban employees with obesity. 22 The study was conducted from 2015 to 2019. Details of the protocol and baseline findings have been reported elsewhere, 22 and the protocol is shown in Supplement 1. The study had a 2-by-2 factorial design. Participants were randomized in a 1:1:1:1 ratio to receive 1 of 4 interventions for 18 months: (1) a lottery-based financial incentive, (2) environmental strategies, (3) both the lottery incentive and environmental strategies, or (4) a usual care (control) intervention with standard employee wellness benefits and weigh-ins every 6 months. All groups received the usual care intervention. After randomization, participants weight loss, and in months 7 to 18, the focus was on maintenance or continued weight loss. After the primary end point of 18 months, participants were followed up for an additional 6 months without any intervention. This study was approved by the institutional review board of the University of Pennsylvania, and participants completed informed consent forms online. This randomized clinical trial follows the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline.

Study Population
Eligible participants were men and women who were aged at least 18 years, working full-time or parttime at 3 large employers in Philadelphia, Pennsylvania, and who had a BMI of 30 to 55 and at least 1 other cardiovascular risk factor. At the time of recruitment, participants also must have as their primary health insurance provider Independence Blue Cross, one of the companies participating in the study. Background information, including race and ethnicity, was collected by self-report to characterize participants' demographic characteristics. Individuals who could not read consent forms or complete surveys in English were excluded. Health-related exclusion criteria were limited to factors that make participation in a weight loss program unfeasible, unsafe, or require more intensive monitoring or that may confound results, 23,24 such as unstable heart disease, serious chronic illness (eg, transplant recipient, terminal illness), substance abuse, or pregnancy.

Recruitment
For this study, we collaborated with 3 large urban employers in Philadelphia, Pennsylvania. Initial outreach to employees used existing communication channels at each site. 22 Interested participants were asked to access the Penn Way to Health (WTH) study platform for prescreening and eligibility ascertainment. WTH is a customizable web-based platform that supports recruitment, consent, randomization, and data collection for clinical trials. 25

Interventions
All interventions were conducted for 18 months. Participants in the 3 intervention groups received a free wireless scale (accurate to within 0.2 lb [0.09 kg]) to submit weights remotely. Participants in the usual care group did not receive wireless scales because it would not be consistent with usual care.

Financial Incentives
The lottery-based incentive group participants were given a weight-loss goal for the first 6 months of 0.5 lb (0.23 kg) a week. For each month from months 7 to 18, they were asked to set a goal to either maintain weight loss or lose more weight. Participants weighed themselves each morning, and their weights were automatically transmitted to the WTH system. Participants received automated verbal and graphic feedback on their progress relative to their goals and potential earnings.
Participants in the lottery group were eligible for a daily lottery prize with an expected value of $3.00 per day if they met their weight goal. Half of the winnings were paid out at the end of each month. To leverage loss aversion and the endowment effect to augment motivation, 26 the other half was held in a virtual account and paid after 6 months if participants met or exceeded their monthly goals.

Environmental Strategies
The environmental change strategy group involved a menu of promising and evidence-based environmental change strategies to promote healthy eating and physical activity, delivered through  Environmental change strategies (tips and messages) were sent to participants in the environmental and combined study groups twice weekly during the first 6 months, and weekly during months 7 to 18. Participants in the environmental strategies groups were also invited to join a private, members-only Facebook group, where group members were invited to share their stories to motivate each other with their weight loss.

Usual Care
Employees at all 3 workplaces were offered a wellness program that consisted of yearly biometric screenings and reimbursements for fitness and weight management program participation (up to $300 per year). Up to 6 visits with a registered dietitian were also included.

Outcome Measures
All participants were weighed in person at enrollment into the study and at the visits at 6, 12, 18, and 24 months. The primary outcome was weight loss at 18 months, and the secondary outcome was weight loss or maintenance at 24 months. Participants completed surveys at baseline and every 6 months, to assess background characteristics and potential covariates and mechanisms of change, including physical activity, 29 cognitive restraint, uncontrolled eating and emotional eating behaviors, 30 stages of change for diet, 31 and general health-related quality of life. 32

Process Measures
Several process measures were used to help interpret the study findings. These included compliance with home weighing in the 3 study groups that had wireless scales, reactions to environmental strategies (ie, text or web surveys), and participation in the Facebook group in the environmental strategy study groups. An end-of-study survey was administered to all participants at the end of their participation.

Statistical Analysis
Participants were randomized in a 1:1:1:1 ratio to 1 of the 4 groups using stratified randomization and a permuted block algorithm with variable block size using the WTH software. Randomization was stratified by workplace, sex, and BMI (30-37.9 vs 38-55). The following prespecified pairwise comparisons were tested at 18 months: (1)  power for each single intervention comparison to control and 87% power for each single comparison with the combined intervention, using the Holm-Bonferroni-corrected level for significance. 33 A 20% dropout rate was assumed to determine the final planned total sample size of 328 participants.
During recruitment, the sample size was increased to 344 because some individuals were unable to set up scales. 22 As a result of a programming error, the 24 participants enrolled after the change in enrollment targets were randomized using a modified simple randomization algorithm that forced equal size groups of 86 participants by closing groups once the target was achieved.
The primary analysis is an intention-to-treat (ITT) analysis comparing the unadjusted mean weight change from baseline to 18 months (in-person weight), between each intervention group and the control group, and the combined group compared with each single intervention group, using a t test and performed at the Holm significance level that adjusts for the 5 primary comparisons. 33 and a group-time treatment interaction was used to examine whether changes in weighing frequency differed between the intervention groups.

JAMA Network Open | Nutrition, Obesity, and Exercise
All hypotheses were analyzed using 2-sided tests. The 5 primary comparisons were tested using the Holm-Bonferroni-adjusted significance level, and all other tests were done at the P < .05 level.
Analyses were conducted using SAS statistical software version 9.4 (SAS Institute, Cary, NC). Data analysis was performed from June to July 2021.

Results
A total of 736 participants completed screening, 390 were eligible, and 344 were randomized across the 4 study groups, 86 in each group. Figure 1 shows the study flow diagram. Further details of recruitment were reported previously. 22 Participant demographic characteristics are summarized in Table 1. Participants had a mean (SD) age of 45.6 (10.5) years and a mean (SD) BMI of 36.5 (7.1) 22 ; 247  a Generalized linear models are adjusted by the randomization strata variables of sex to employer and initial body mass index to study group to and baseline participant characteristics of age to race to annual household income to education to baseline weight to marital status to household size and stage of change.  case cohort (eTable 1 in Supplement 2). There were no significant interactions for the incentive vs nonincentive groups by sex, age, race, education, income, household size, BMI, or stages of change (Figure 2A) or environmental strategy vs no-environmental strategy groups ( Figure 2B).
eTable 2 in Supplement 2 shows the ITT intervention effects on the exploratory outcomes of total physical activity, cognitive restraint, uncontrolled eating, emotional eating, and SF-36 General Health score. For the 5 prespecified pairwise group comparisons, only SF-36 General Health score had a positive effect, with scores increasing by a mean of 5.6 points (95% CI, 0.7-10.6 points) in the environmental strategy group compared with the usual care group and 5.5 points (95% CI, 1. 8-9.3 points) in the incentive group plus usual care group combined.
As shown in eTable 3 in Supplement 2, the per-protocol analysis found that the effect for the incentives-only group was larger than in the ITT analysis, and the effect for the environmental strategies-only group was also larger than in the ITT analysis, but the difference was not significant in adjusted analysis. Other comparisons (eFigure 1 and eFigure 2 in Supplement 2) were not significantly different between groups or combinations of groups in the adjusted analyses.

Process Findings
After the first week, there was a steady decrease in home self-weighing in all 3 groups with wireless scales (Figure 3); however, the 2 incentive groups weighed in more frequently than the environmental strategy group during the intervention period. In the generalized estimating equation model testing a time-treatment interaction, no significant differences were found between study groups in the rate of change over time (slope) of weigh-in frequency; however, participants in the incentive alone group and the combined group self-weighed a mean of 1.6 days per week (95% CI, 1.0-2.3 days per week) and 1.4 days per week (95% CI, 0.8-2.0 days per week), respectively, more often than the environmental strategies group. All 3 intervention groups had similar weekly weigh-in frequencies by 24 months (eTable 4 in Supplement 2).
The individually tailored text messages in the environmental strategies were well received.
When asked whether they had used the tips to make recommended environmental modifications, a mean of 72% of respondents (range, 27%-96% of respondents) said they had tried each tip. Only 49 participants (28% of the environmental strategies groups) participated in the Facebook group.
Responses to the end-of-study survey (207 participants [60%]) indicated that most participants were satisfied with the study procedures (80% were very much or somewhat satisfied), and those who received wireless scales planned to use them after the study (82% said very much).  Only one-third said they met their weight loss goal partly or completely. Some respondents indicated that they felt a need for more guidance or a more detailed weight loss plan.

Discussion
The Healthy Weigh Study recruited a racially diverse, mostly female, employee population with obesity to a weight loss trial with 18 months of active intervention and a 6-month follow-up period.
Participants were randomized to receive financial incentives for achieving weight loss goals, customized environmental strategies, a combined incentives and environmental strategies group, or usual care. At the end of active study period, none of the study groups achieved significantly greater weight loss than the usual care group, and the results were similar 6 months later. The highest weight loss occurred in the incentive groups, with 7.1 lb lost over 18 months. All 3 intervention groups sustained approximately a 4 lb weight loss at 24 months.
This study differs from previous employer-based weight loss trials rooted in behavioral economics, in that all participants had BMIs in the obese range (mean BMI, 36.5), and the intervention period was substantially longer than in previous studies. A systematic review of 47 workplace weight loss programs, most of them low-intensity as in this study, showed that cluster randomized trials of similar duration also found modest weight losses. 21 Some short-term incentive interventions achieved greater initial weight loss of 10 to 14 lb 12,14 that were not sustained after 4-to 8-month interventions. 34 Other behavioral economics-based strategies, such as deposit contracts, achieved low participation rates. 35 A recent systematic review of strategies to improve workplace policies and environments to reduce risk behaviors, including obesity, noted that the available evidence is "sparse and inconsistent." 36

Strengths and Limitations
This study had both strengths and limitations. The use of wireless scales to objectively track weight over time is a strength, and as is the diverse study sample. Limitations include the study being conducted in urban workplaces without cafeterias and possible selection bias by study participants.
It is possible that the design of the incentives made them less effective than we had hoped. 37 There was a delay between earning incentive payments and receiving the funds. Also, general study payments for enrollment and completion of measures totaled $300 across the course of the study, potentially muting the incremental effect of offering incentives tied to weight loss.
A recurrent theme in end-of-study surveys was that participants felt they would have benefited from more intensive guidance, such as ongoing counseling or coaching. Also, environmental manipulations may need to be more intensive to promote greater weight loss success. Furthermore, the power calculations for this study assumed a higher average weight loss than was achieved in the intervention groups.

Conclusions
Both initial and sustained weight loss remain substantial challenges to improve health and reduce risk of major chronic diseases. In the Healthy Weigh trial, incentives and environmental strategies led to modest but nonsignificant improvements in weight loss. From a translational standpoint, benefits designs could consider incorporating ongoing financial incentives for weight loss among employees with obesity, while linking online support to more intensive personalized interactive approaches.