Almost half of global adults have attempted to lose weight in recent years. Most people use their own diet and exercise plans, and they use websites and smartphone applications to track their progress. However, over 45\% of weight loss application users quit the applications, and their weight loss goals due to lack of desired features, perceived lack of self-control, and due to the time-consuming and tedious nature of dietary tracking. The theory-based strategies of stimulus control, rewards and social support can address these challenges. In this dissertation, we investigate the effectiveness of these three strategies in supporting user adherence to dietary tracking and behavior change. We used a user-centered design approach to determine user requirements for the implementation of these strategies. We then implemented the strategies and evaluated user experiences and efficacy through field studies.
For the stimulus control strategy, an application to track causes of negative eating behaviors (cues) was developed. After identifying these cues, users were presented with recommendations for healthier behaviors to use. The stimulus control strategy led to a 3 times (3x) higher adherence to dietary tracking compared to a control group, and users achieved their calorie goals 52% of the time vs 39% for the control group. User satisfaction with stimulus control was 65%. Social support was provided through a group fitness application that offered a structured eating and exercise plan to groups of less than 10 people, and the strategy resulted in a 2.3 times (2.3x) improvement in adherence to fitness goals from baseline, and scored 60.8% in user satisfaction. To assess the impact of rewards, a game with cash and virtual rewards was implemented. Users played the game irregularly and felt the strategy was unsuitable for consistent, long term tracking, leading to a user satisfaction score of 44\%.
These results reveal that supporting users to suppress triggers of negative behavior and recommending alternative healthy behaviors, as well as providing social support may be effective for supporting adherence to weight loss behavior change.