RIO DE JANEIRO—Glowing with pride as he spoke about his infant son’s strict daily nutritional regimen, U.S. Olympic swimmer Michael Phelps explained to reporters Wednesday that his 3-month-old son, Boomer, consumes 12,000 calories of breast milk per day. “Boomer needs at least 2,000 calories during every feeding, and we usually have to feed him six to seven times a day,” said Phelps, adding that his child devours roughly 15 times the recommended daily caloric intake for the average 3-month-old male baby of his size and age. “He usually starts the day off with a breakfast of 90 fluid ounces of breast milk—about 10 bottles’ worth—and we give him 10 more bottles each for lunch and dinner. And then throughout the day he’ll have another 10 or 15 bottles of breast milk here and there as a snack. Obviously, this type of diet isn’t meant for all babies, but given how many calories he burns off in the crib, he needs that much breast milk to maintain his 12-pound frame.” Phelps added that his fiancée, Nicole Johnson, has to maintain a strict 55,000-calorie-per-day diet in order to keep Boomer properly nourished.