Background Intermittent fasting (IF) has gained popularity in recent years for its effect on weight loss and supposed additional health benefits, such as a positive effect on body composition and metabolic markers. Mobile apps can act as platforms that help deliver dietary interventions by improving adherence and motivation. Although the effect of IF on weight loss has been demonstrated in earlier trials, there is not much research about the engagement and weight loss results with IF apps. Objective Our main objective was to compare how a nudging platform (including smart scales) influences engagement (the extent to which users interact with the app measured by the number of active days) with the app among users who had obesity at the beginning of use. The secondary objectives were to evaluate the body weight changes among active and nonactive users and, finally, to evaluate the body composition changes of users possessing smart scales during app usage. Through this study, we hope to provide (1) more insight into how nudging (using smart scales as a nudging platform) is associated with engagement with the mobile app, (2) how engagement with the mobile app is associated with weight loss, and (3) how IF is associated with body composition. Methods We performed a retrospective analysis of data from 665 users with obesity (BMI≥30) who started using the IF app DoFasting. Of them, 244 used body composition scales that estimated body fat and body muscle values. Users were stratified into engagement groups in accordance with their activity ratio (number of active days divided by the total time of use). Baseline and final users' weight (in kg), body fat (in %), and body muscle (in %) were compared. Results Our findings suggest an association between the nudging platform (smart scales) and better engagement with the app. Smart scale users had a significantly higher activity ratio than regular users. Additionally, active DoFasting users lost significantly more weight. Further, body composition analysis showed that app usage might be related to body fat loss and an increase in muscle mass. Conclusions We found a possible association between the nudging and gamified elements and higher app engagement. Additionally, increased app engagement is associated with increased weight loss. Thus, nudging and gamified elements of mobile health apps, such as interactive tools, goals, challenges, and progress tracking, are suggested to affect engagement positively and should be investigated further in future research. Finally, the IF regime delivered through the DoFasting app might be related to the body muscle mass gain and reduced fat mass.

Background The purpose of this study was to investigate the efficacy of intermittent fasting (IF) guidance, delivered through a smartphone application, in terms of engagement and weight loss. Methods We performed a retrospective chart-review study of all consecutive users with overweight or obesity of the DoFasting mobile application, which integrates IF solutions for people looking to lose weight. Users with overweight and obesity at the beginning of application use, who met the inclusion criteria (entered their gender, height, and starting weight; had more than one weight entry; used the app for at least a month; had at least one active day per week with valid app-related activities) and used the application for weight loss were included in the study. Results The final study cohort comprised 22,022 consecutive users. The short-term cohort comprised 17,221 users (8585 females and 8636 males), while 4801 users (2983 females and 1818 males) were in the long-term cohort. Long-term active users of the application lost a statistically significant amount of weight over the study period and lost more than inactive users did (2.2 [3.5] vs 1.4 [3.2], p < 0.0001; the results are shown in kilograms as medians with the interquartile range in brackets). Active and long-term users were also more likely to reduce their BMI class (p < 0.05) in comparison to non-active short-term users. A multiple regression model showed that the total length of use and active days were the most significant predictors of weight loss. In-app activities such as total fasting hours, weight logging, completing challenges, and providing feedback were also statistically significant predictors of weight loss with varying contributions. Conclusion We found that the DoFasting mobile application that implements IF is an effective tool for weight loss if used actively and sufficiently. Trial registration This retrospective chart review study was approved by BRANY IRB in January 2022 (study ID.: 22‐08‐034‐939).

BACKGROUND Intermittent fasting has gained popularity in recent years for its effect on weight loss and supposed additional health benefits, such as a positive effect on body composition and metabolic markers. Mobile applications (apps) can act as platforms that help deliver dietary interventions by improving adherence and motivation. Although the effect of intermittent fasting on weight loss has been demonstrated in earlier trials, there is not much research about the engagement and weight loss results with intermittent fasting apps. OBJECTIVE To compare how engagement with the DoFasting application influences the weight loss of the users that had obesity at the beginning of use. The secondary objectives were to evaluate the body composition changes of users possessing body composition scales during the application usage time. METHODS We performed a retrospective analysis of data from 665 obese users of an intermittent fasting application DoFasting. Of those, 244 used body composition scales that estimated body fat and body muscle values. Users were stratified into engagement groups according to their activity ratio. Starting and final users' weight (kg), body fat (%), and body muscle (%) were compared. We also created logistic regression models showing how engagement with the app predicted losing at least 5% of body weight, 1% of body fat, or gaining 1% of body muscle. Finally, we have checked how using body composition scales affected engagement. RESULTS The main findings of our study are that active DoFasting users lost statistically significant amounts of weight in all BMI groups (p < 0.05) and that active users have more than three times higher chance of losing at least 5% of weight (95 % CI [1.994 – 4.956]), more than two and a half times higher chance of losing at least 1% of body fat (95 % CI [1.199 – 5.233]), and more than two times higher chance to gain at least 1% body muscle mass (95 % CI [1.053 – 4.664]), as indicated by regression analysis. CONCLUSIONS DoFasting appeared effective for weight loss with intermittent fasting in the short term. However, active engagement was necessary for better results. Gaming elements in mobile health apps are suggested to appeal to users and help engagement. CLINICALTRIAL This retrospective chart review study was approved by BRANY IRB in January 2022 (registration ID.: 22‐08‐034‐939).