Sounds like it's exactly the same "magic" as exercise and calorie restriction. If the body has more energy available than it needs for normal function, it'll us

Sounds like it's exactly the same "magic" as exercise and calorie restriction. If the body has more energy available than it needs for normal function, it'll use as much as it can and eventually that use goes to things like general inflammation, cancer, and autoimmune disease. If you use available energy to exercise, simply eat less, or disrupt your body's ability to actually use all the excess food you feed it with drugs, then it won't be able to do those bad things and will only maintain essential function. Obviously, if you restrict too much, you starve. Animals in a state of nature seem to automatically find the right balance and eat roughly exactly what they need. Animals placed into situations in which food is nearly costless, effectively infinite, and you don't need to be active except to the extent you do it freely for recreation, seem to struggle. Humans suffering from diseases of civilization are one such example, but human pets and livestock seem to have the same problems. Presumably, lab rats are basically like that, too. Life in a plastic cage with no predators and food given to you directly by gods is not very similar to life in the wild.