Long-term effects of the use of a step count-specific smartphone application on physical activity and weight loss: a randomized clinical trial (Preprint)

BACKGROUND Some studies on weight loss promotion using smartphone applications (smartphone app) including mobile applications have shown a weight loss effect, but not an increase in physical activity, and they have not been rigorously examined for longer periods. OBJECTIVE To assess whether the use of a smartphone app will increase physical activity and reduce body weight. METHODS In this parallel randomized clinical trial, participants recruited between April 2018 and June 2019 were randomized in equal proportions to a smartphone app group (n=55) or control group (n=54). The intention-to-treat approach was used to analyze the data from December 2019 through November 2021.　Before the intervention, an hour-long lecture on weight loss instruction and increasing physical activity was conducted once for both groups. Participants in both groups were instructed to weigh themselves immediately after waking up at least once daily from the start of the intervention. Monthly e-mails were sent advising the participants on how to lose weight and increase physical activity in order to maintain or increase motivation in both groups. Participants in the smartphone app group were instructed to launch the app at least once a day to check their step count and rank. The primary outcome was daily accelerometer-measured physical activity (step count) and secondary outcomes was body weight. RESULTS The 109 participants had a mean (standard deviation) age of 47 (8) years. At baseline, the mean (standard deviation) daily total steps were 7259 (3256) for the smartphone app and 8243 (2815) for control groups, respectively. After the 32-week intervention period, the step count per wear time was significantly higher in the smartphone app group than in the control group [average difference (95%CI): 65 (30 to 101) vs. -9 (-56 to 39), p=0.042]. The weight loss was -2.2 kg (-3.1%) in the smartphone app group and -2.2 kg (-3.1%) in the control group, with no significant difference between the groups. During the intervention period, the step count per wear time on Saturdays [615 (545 to 684) vs. 554 (483 to 624), p=0.006] and Sundays [623 (553 to 694) vs. 556 (485 to 627), p=0.004] was significantly higher in the smartphone app group than in the control group. CONCLUSIONS In this trial, the smartphone app group showed increased physical activity, especially on weekends. However, this increased physical activity did not lead to weight loss. CLINICALTRIAL UMIN000033397 https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000037956&type=summary&language=J