Background:Smartphones present a near-ubiquitous channel through which structured lifestyle change can reduce risk or progression of the most common noncommunicable diseases. We explored whether a digital structured lifestyle program enhances weight loss.Methods:We randomized overweight and obese participants attending a four-month lifestyle change program to either standard weekly coaching sessions (controls), or standard treatment supplemented with a digital therapeutic mobile application (intervention). Changes in body mass index after four months were the main outcome measure. Odds ratios of achieving 5% weight loss were estimated with unconditional logistic regression.Results:Of 234 eligible persons, 146 (62%) agreed to participate, were block-randomized, showed up for the baseline measures, and constituted the intention-to-treat (ITT) sample ( n = 95 intervention group, n = 51 control group). In the intervention group, 70 (74%) downloaded the mobile application and completed the program (intervention per-protocol). Significant weight loss and BMI reduction were observed for both the intention-to-treat intervention group ( P < 0.05, P = 0.01) and the per-protocol intervention group ( P < 0.0001, P < 0.0001). For the intervention per-protocol group, the odds ratio of achieving 5% weight loss, compared to not treated per-protocol, was 3.3 (95% CI 1.3-8.2), adjusting for age and weight at baseline.Attendance to weekly coaching sessions decreased by 18% during the program in the control group while it increased by 3% amongst the per-protocol group ( P = 0.004).Conclusions:These preliminary findings support the benefit of a digital therapeutic to enhance weight reduction and attendance in a structured lifestyle change program. Larger trials of longer duration are needed to confirm these findings.