Abstract P399: The Effect of Self-Monitoring of Diet, Weight and Steps and Adherence to Diet, Fat and Physical Activity Goals on Weight Loss at 12 Months: Smarter RCT

Abstract

Introduction: Self-monitoring (SM) is the core of behavioral weight loss. Efficacy evidence for mHealth to improve SM adherence and impact weight loss outcomes is limited. Purpose: Examine associations among diet, weight, and physical activity (PA) SM and adherence to diet, fat and PA goals on weight loss at 12 mos in adults with overweight or obesity. Methods: SMARTER was a single-site, 2-arm weight loss trial. We randomized adults with (BMI) 27-43 kg/m 2 to diet, weight, and PA SM plus tailored feedback messages (SM+FB, n=251) or SM alone (n=251). The SM+FB group received feedback messages via the SMARTER app on diet daily, PA every other day and weight weekly. The study provided Fitbit Charge 2™ for PA, smart scales for weight and Fitbit app for diet. Participants received individualized daily calorie/fat goals (based on sex & weight) and incremental weekly PA goals to reach ≥300 min/wk of moderate- and vigorous-intensity PA. Staff measured weight at baseline, 6 and 12 mos. Diet SM was the % of days with ≥50% of calorie goal recorded. Weight SM was the % of days with weight recorded. PA SM was % of days with ≥500 steps. Calorie goal adherence was % of days with ≥85% and <115% of calorie goals and fat goals as ≤25% of calorie goals. PA goal adherence was the average % of weekly MVPA meeting the PA goal for ≥4 days/wk. Weight loss at 12 mos was computed as the % of change in weight from baseline to 12 mos relative to baseline weight. We compared diet, weight and PA SM and adherence to calorie, fat and PA goals by treatment assignment using Wilcoxon rank-sum tests. The effect of diet, weight and PA SM and adherence to calorie, fat and PA goals on weight loss at 12 mos was examined using separate linear regression models considering treatment assignment and interaction effects. Results: The sample (N=502) was 82% white (n=414), 79% female (n=399), on average 45.0±14.4 years of age with a mean BMI of 33.7±4.0 kg/m 2 . Treatment arms were similar on % days of weight and PA SM and % days adherent to calorie, fat and PA goals (p≥.05); however, the SM+FB group had greater % days of SM diet than the SM group (58.9 [24.7, 84.9] vs. 41.1 [14.0, 81.9]; P=.01). Weight loss at 12 mos was significantly associated (reported as b [95% CI]) with higher % of days of SM diet (-0.10 [-0.13, -0.08]), weight (-0.12 [-0.14, -0.09]) and PA (-0.10 [-0.13, -0.07]) and % days adherent to calorie (-0.06 [-0.11, -0.01]) and fat goals (-0.11 [-0.20, -0.02]) and average % days adherent to PA goals (-0.04 [-0.06, -0.02]). The effect of treatment assignment and its interactions with SM of diet, weight and PA and adherence to calorie, fat and PA goals on weight loss at 12 mos were not significant. Conclusions: In this study, SM of lifestyle behaviors and adherence to diet and PA goals were associated with better weight loss at 12 months and did not depend on treatment group assignment, suggesting that the mHealth intervention did not enhance adherence sufficiently to affect weight loss outcomes.