The goal of this retrospective observational study is to evaluate the real-world durability of weight loss among adults with overweight or obesity who used the Key to Health breath-biofeedback mHealth program. The main questions it aims to answer are:
1. What is the mean percent total body weight loss (TBWL%) at 104 weeks after program start?
2. What are the TBWL% estimates at 12, 24, and 52 weeks, and what proportion of users achieve clinically meaningful weight loss (≥5% and ≥10%) at 52 and 104 weeks (observed case)?
Users initiated the program between Nov 2018 and Apr 2023; follow-up data (weights/engagement) were collected through Apr 2025 to allow up to 104 weeks of observation.
There is no randomized comparison group. Participants will not be asked to do anything beyond normal app use; the study will analyze existing, de-identified weight and engagement data collected during routine program use.