JMIR Publications

ABSTRACT

Background:

Self-monitoring (SM) is the centerpiece of behavioral weight loss treatment, but efficacy of smartphone-delivered SM feedback has not been tested in large, long-term randomized trials.

Objective:

Establish efficacy of providing remote feedback to self-monitoring of diet, physical activity and weight SM on improving weight loss outcomes.

Methods:

DESIGN: Compared SM plus feedback (SM+FB) to SM only in a 12-month randomized controlled trial. SETTING: Single site, population-based study in southwestern Pennsylvania, USA conducted between 2018 and 2021. PARTICIPANTS: Smartphone users age ≥18 years, able to engage in moderate physical activity (PA), with a mean body mass index (BMI) between 27 and 43 kg/m2). INTERVENTION: All participants received a 90-minute 1:1 in-person behavioral weight loss counseling session addressing behavioral strategies, establishing participant’s daily dietary and weekly PA goals, and instructing on use of PA tracker (Fitbit Charge 2™), smart scale, and diet SM app. Only SM+FB participants had access to an investigator-developed smartphone app that read SM data, selected tailored messages sent to smartphone up to 3 times daily. The SM only participants did not receive any tailored feedback based on SM data. MAIN OUTCOME(S) AND MEASURE(S): The primary outcome was percent weight change from baseline to 12 months. Secondary outcomes included engagement with digital tools (e.g., monthly percentage of feedback messages opened and monthly percentage of days adherent to calorie goal).

Results:

RESULTS: Participants (N=502) were on average 45.0 (SD 14.4) years old with BMI of 33.7 (SD 4.0) kg/m2. The sample was 79.5% female (n=399) and 82.5% white (n=414). At 12 months, retention was 78.5% (n=394) and similar by group (SM+FB: 80.5%, SM: 76.5%, P=.277) There was significant percent weight loss from baseline in both groups (SM+FB: -2.12%, 95% CI -3.04% to -1.21%, P<.0001; SM: -2.39%, 95% CI -3.32% to -1.47%; P<.0001), but no difference between the groups (-0.27%; 95% CI -1.57% to 1.03%, t-value=-0.41, P=.681). Similarly, 26.3% of the SM+FB group and 29.1% of the SM group achieved ≥5% weight loss (chi-square value=0.49, P=.485). A one percent increase in FB messages opened was associated with 0.10 greater percent weight loss at 12 months (b=-0.10; 95% CI -0.13 to -0.07; t=-5.90; P<.0001). A one percentage increase in FB messages opened was associated with 0.12 greater percentage of days adherent to the calorie goal per month (b=0.12; 95% CI 0.07 to 0.17; F=22.19, P<.0001).

Conclusions:

There were no significant between group differences in weight loss; however, results suggest that the use of commercially available digital self-monitoring tools with or without feedback can result in a clinically significant weight loss in over 25% of participants. Future studies need to test additional strategies that will promote greater engagement with digital tools. Clinical Trial: The study is registered with Clinicaltrials.gov (NCT03367936).