I just went off Metformin (calorie restrictor that causes weight loss) in favor of a higher protein diet. Metformin seems to works against increasing muscle-mass. My experience sort of reinforces your point, caloric restriction = longer life, protein enhancement = better life quality. I'm searching for the happy medium, which may be increasing protein/exercise/muscle mass to the point of higher weight loss? Note: I'm carb-restricted but not carb-free.