Accepted for/Published in: JMIR mHealth and uHealth
Date Submitted: Mar 16, 2020
Date Accepted: Apr 15, 2021
Assessing the contribution of self-monitoring through a commercial weight loss app: mediation and predictive modeling
ABSTRACT
Background:
Electronic self-monitoring technology has the potential to provide unique insights into important behaviors for inducing weight loss.
Objective:
To investigate the possible effects of electronic self-monitoring behavior (using the commercial Lose It!TM application) and weight loss interventions (with differing amounts of counselor feedback and support) on 4 and 12-month weight loss.
Methods:
We compared the results from two interventions. Counselor-initiated (CI) treatment participants received early, consistent support from interventionists, and self-paced (SP) treatment participants received assistance on request. Participants were encouraged to self-monitor diet and exercise with the Lose It!TM application or website. We examined logging trends throughout the study for associations between intervention assignment and app usage. We conducted a mediation analysis under the counterfactual framework of the intervention assignment on weight loss through multiple mediators: app usage (calculated from the first principal component of electronically collected variables), number of weigh-ins and 4-month weight change. Prediction models were created based on linear regression and PCA from the first 4 and 8 weeks of the study to predict weight loss at 4 and 12 months; accuracy was measured using cross-validation.
Results:
On average, CI group participants used the app more frequently than the SP group. The first principal component (PC) represented app usage frequencies, the second represented calories recorded, the third represented reported exercise frequency and exercise caloric expenditure. We found that 4-month weight loss was partially mediated (41.1%) through app usage (i.e. first component) and number of weigh-ins. However, 12-month weight loss was almost fully mediated (94.8%) by 4-month weight loss. Linear regression using app data from the first 8 weeks, number of self-weigh-ins at 8 weeks, and baseline data combined explained about 30% of the variance in 4-month weight loss. App usage frequencies (1st PC, P = .0014), self-monitored calorie intake (2nd PC, P =.0012), and frequency of self-weighing at 8 weeks (P =.008) were important predictors of 4-month weight loss. Predictions for 12-month weight with the same variables produced an R2 value of 5%; only the number of self-weigh-ins was a significant predictor of 12-month weight loss. Using 4-month weight loss as a predictor the R2 was 31%. Self-reported exercise did not contribute to either model (4 months: P =.77, 12 months: P = .15).
Conclusions:
We showed that app usage and daily reported caloric intake have substantial impact on weight loss prediction at 4 months. Our analysis did not find evidence of association between participant self-monitoring exercise information and weight loss. Since 12-month weight loss was completely mediated by 4-month weight loss, intervention targets should focus on promoting early and frequent dietary intake self-monitoring and self-weighing to target early weight loss goals leading to long-term success. Clinical Trial: ClinicalTrials.gov identifier NCT 02063178; https://clinicaltrials.gov/ct2/show/NCT02063178
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