Mark Klion, a sports medicine doc Mount Sinai Medical Center in New York.
"If you eat fewer calories than you burn exercising, you lose weight. But an athlete like Phelps, who exercises up a storm, has to worry about eating enough to replenish the scads of calories he’s burned."
If he doesn’t, Klion explains, his “body won’t recover, the muscles will not recover" meaning he will have no energy