Athletes need to consume adequate energy during periods of high-intensity and/or long-duration training to maintain body weight and health and maximize training effects. Low energy intakes can result in loss of muscle mass, menstrual dysfunction, loss of or failure to gain bone density, an increased risk of fatigue, injury, and illness and a prolonged recovery process.

Teen athletes have unique nutrition needs. Because athletes work out more than their less-active peers, they generally need extra calories to fuel both their sports performance and their growth. Depending on how active they are, teen athletes may need anywhere from 2,000 to 5,000 total calories per day to meet their energy needs.