The older generation often said that if you don't work, you don't have to eat so much. Is this correct?

From the perspective of energy consumption, if you don't work and have a small amount of activity, your physical energy consumption will naturally be less, and the physical energy and energy that need to be supplemented will be relatively less. So don't eat too much food.

From the principle of distribution according to work, more work and more pay, this statement can also make sense. Get more with more work, get less with less work or get for nothing. These are generally accepted views.