At different times in a man's life the food has different effects(影响) on his body.

    Among children  is quickly changed to the power to run and play games. Most of a young man's food is spent on growing . We grow upwards only during the first twenty years of our lives, not later. Working men get their strong bodies from their food; and if they work , they do not get fat. Office workers eat well and  down a lot, and may begin to grow fat when still quite young. Many older people try to work much and walk often. Perhaps the most difficult time is when a man reaches sixty years of age. His body and mind  rested, without much work or interest. That is when food changes quickly to fat.