The only way for a rich man to be healthy is, by exercise and abstinence, to live as if he was poor.

Comfort removes the constraints that used to do the work automatically. When walking is optional, food is abundant and nothing requires physical effort, the habits that once came with circumstances have to be chosen and maintained instead. There is nothing enviable about having no choice; going without because you must is hard in ways that voluntary restraint is not.

Reintroduce one constraint you no longer face: walk the distance you would normally drive, eat at set times, keep something out of the house rather than resisting it. Constraints applied on purpose work almost as well as the ones life used to impose.