There have been many efforts to rectify lifestyles that contribute to obesity using a variety of methodologies in heterogeneous settings, but effective and sustainable interventions that are suitable for children are still needed. We developed a smartphone application called “HAPPY ME” for guiding health behavior decisions, which employs gamification and self-monitoring strategies. The aim of this paper is to outline the rationale and methods for the development and feasibility test of “HAPPY ME”.

The study consisted of two phases: 1) description of theory-based conceptual framework and rationales for smartphone application development and 2) outline of a pre- and post-test design in 4^th-6^th grade of healthy elementary school students for 4 weeks. The students will be delivered missions or messages on a daily basis, which is to stretch the knowledge and skills for action. They will simultaneously be engaged in self-monitoring their eating and physical activities to clear daily quests. To measure acceptability and feasibility we will monitor usability, compliance, and satisfaction for a 4-week study period and evaluate the intervention effects on self-efficacy, readiness, and intention to engage in healthy behavior.

The results of the feasibility study will show whether the smartphone application “HAPPY ME” for children is acceptable, as well as if it is usable and feasible for self-directed health management. The results will provide preliminary evidence of the effectiveness of smartphone application-supported child behavioral modification for child obesity prevention and management.