Mackenzie Wolfson, a natural athlete (second from left) and accomplished tennis player and a member of her school's varsity softball team, takes a break on the sidelines of a field hockey game on a hot afternoon with her teammates at Camp Shane, Catskill Mountains, New York. (From the book What I Eat: Around the World in 80 Diets.) The caloric value of her typical day's worth of food in July was 1,700 kcals. She is 15; 5 feet nine inches tall, and 299 pounds.