I feel like we basically know what we should be doing to avoid many illnesses. Get better sleep, be more active, eat better, etc. The problem is almost always finding the willpower to make the changes and maintain the good habits long term.
Instead, let us change our environments to better suit the primates we still are.
The cheapest food options are the unhealthiest. Hours of overtime and long commutes prevent sufficient sleep. And exercise is considered a leisure activity.