Barring acts of God / nature, such as genetic disease, the formula for health is pretty simple and straightforward -- nutrition and exercise.
Nutrition is a matter of dietary composition (protein, carbs, fat, vitamins and minerals, and hydration), food quality (natural, whole, ripe, fresh, local, organic), and eating habits (caloric needs, hunger, appetite, portion size).
Exercise is fundamentally about frequent intense effort focused on developing cardiovascular (endurance) and muscular (strength) capacity without injuring yourself.
But if health was happiness, then all professional athletes would be happy, which obviously is not the case. Conversely, some of the most radiant beings you'll ever encounter are the kids in the cancer ward. They have lost their health, but they've transcended their physical identities to something much more subtle and pure. This is an exceptional case. So while it's possible to be happy even in a state of ill health, it's unlikely.
BODY – MIND – SPIRIT