Women athletes who seek to become lighter and faster by dieting may merely jeopardize their competitive chances, according to a nutrition consultant to the U.S. Olympic swimming team.
"Dieting during intensive training does nothing but starve a hard-working machine. Instead of losing weight, the body defensively conserves fat and burns the muscle tissue athletes need to perform," said Jackie Berning, a registered dietitian.
Further, the key nutrients iron and calcium are often lost during dieting regimens, which can lead to iron-deficient anemia and weakened bones, said Berning.
"We often see this counterproductive dieting in the lean-profile sports, such as running, gymnastics, diving or figure skating," she said. "It's like trying to drive a Porsche for 100 miles at top speeds on a gallon of gas. You can't operate at peak performance without enough fuel. It is important to maintain balance in the diet and eat the right number of calories to fuel the exercise."
The rule of thumb is three-two-four-four: three servings of milk or dairy foods, which are high in calcium, two of iron-rich meats or meat alternates, and four each from the fruit/vegetable and bread/cereal groups.
Calorie levels for athletes should be set according to the type of activity because most of their calories are burned during exercise, said Berning. On average, runners need 425 additional calories for every 30 minutes of exercise. Cyclists require 375 calories for the same period, and swimmers need 300.