The paper Developing Theory-Driven, Evidence-Based Serious Games for Health: Framework Based on Research Community Insights by Verschueren and colleagues provides a well-researched framework for developing any serious game and especially one for health/wellbeing purposes.
Their research into efficacy and best-practices in game development is poured into a framework with five stages
It all starts with asking the right questions, finding out what is relevant to your goals and preferable forming a hypothesis & thereby setting metrics, early on in development. Gather data from research, interviews and observation. Get your players, health care professionals and other stakeholders involved but not every step of the way begs the same kind of involvement. Test, iterate, test, iterate… and always keep your eyes on what you’ve determined as your goal and what was relevant to this. And finally, if you can, test your hypothesis.
I really recommend this paper – great read with good guidelines to follow!