Background: Evaluating the quality of mHealth apps for weight loss and weight management is important to understand whether these can be used for obesity prevention and treatment. Recent reviews call for more research on multi-dimensional aspects of app quality, especially involving end-users, as there are already many expert reviews on this domain. However, no quantitative study has investigated how lay persons see popular apps for weight management and how they perceive different dimensions of app quality. Objective: To explore how lay persons evaluate the quality of six free weight management apps (MyDietCoach, SparkPeople, Lark, MyFitnessPal, MyPlate, MyDietDiary), which achieved the highest quality ratings in a related and recent expert review. Methods: A user-centered study was conducted with 36 employees of a Lebanese university. Participants enrolled in the study on a rolling basis between October 2016 and March 2017. Participants were randomly assigned an app to use for two weeks. App quality was evaluated at the end of the trial period using the Mobile App Rating Scale (user version, uMARS). uMARS assesses the dimensions of 'engagement', 'functionality', 'aesthetics', 'information', and 'subjective quality' on 5-point scales. Internal consistency and inter-rater agreement were examined. The associations between uMARS scores and background characteristics were also explored using non-parametric tests. Analyses were completed in November 2017. Results: Overall, the six apps were of moderately good quality (Md uMARS score=3.6, IQR=0.3). The highest total uMARS scores were achieved by Lark (M=4.0, SD=0.5) and MyPlate (M=3.8, SD=0.4), which also achieved the highest subjective quality scores (Lark: M=3.3, SD=1.4; MyPlate: M=3.3, SD=0.8). 'Functionality' was the highest-rating domain (Md=3.9, IQR=0.3), followed by 'aesthetics' (Md=3.7, IQR=0.5), 'information' (Md=3.7, IQR=0.1), and 'engagement ' (Md=3.3, IQR=0.2). 'Subjective quality' was judged low (Md=2.5, IQR=0.9). Overall, 'subjective quality' was strongly and positively related (p<0.001) with total uMARS score (rho=0.75), 'engagement' (rho=0.68), 'information' and 'aesthetics' (rho=0.60), but not 'functionality' (rho=0.40, p=0.02). Higher 'engagement' scores were reported among healthy (p=.003) and obese individuals (p=.034), who also showed higher total uMARS (p=.038), and 'subjective quality' (p=.047) scores. Conclusion: Even if the apps were considered highly functional, they were relatively weak in engagement and subjective quality scores, which indicate a low propensity of using the apps in the future. As engagement was the sub-domain most strongly associated with subjective quality, app developers and researchers should focus on creating apps that are engaging, holding constant the functionality, aesthetics, and information quality. The tested apps (in particular Lark and MyPlate) were perceived as more engaging and of higher quality among healthy, obese individuals, making them a promising mode of delivery for self-directed interventions...