i never heard anybody say that having less muscle will make you live longer. it may be true but i never heard about it. i hope whoever studied this relationship has controlled for fat mass. that is a smaller person obviously will live longer than a bigger person but probably not because they have less muscle but because they eat less.

eating less does make you live longer. not only because you avoid diabetes but because your metabolism slows DRAMATICALLY when you eat less. my heart rate goes down by a THIRD when i diet. although we don't die from the heart mechanically wearing out it would be logical to assume that when metabolism slows damage accumulates slower.

so basically if you want to live as long as possible - eat less and keep your waist down to a small size.