Fat also fuels working muscles. In fact, it's a more concentrated energy source. And it performs other body functions, such as transporting fat-soluble vitamins and providing essential fatty acids. For good health, consume fat as one source of fuel. Rather than try to eat almost "fat-free," be smart: low in saturated fat and trans fat, and moderate in your fat intake.
For energy, fat helps power activities of longer duration such as hiking or marathon running. Because fat doesn't convert to energy as fast as carbohydrates, fat doesn't power quick energy spurts such as returning a tennis serve or running a 100-yard dash.
Unlike glycogen, fat needs oxygen for energy metabolism. That's why endurance sports, fueled in part by fat, are called aerobic activities. "Aerobic" means with oxygen, and aerobic activities require a continuous intake of oxygen. The more you train, the more easily you breathe during longer activity; the oxygen you take in helps convert fat to energy.
No matter where it comes from—carbohydrates, proteins, or fats—your body stores extra energy as body fat. These fat stores supply energy for aerobic activity. Even if you're lean, you likely have enough fat stores to fuel prolonged or endurance activity. You don't need to eat more fat!
For Athletes: How Much Fat?
Advice for athletes is the same as that for all healthy people: eat a diet low in saturated fat, trans fat, and cholesterol and moderate in total fat. To get enough calories for sports, yet not too much fat, 20 to 35
percent of your total calories from fat is a good guideline. Most of your food energy should come from carbohydrates. With a high-fat diet your carbohydrate or protein intake may come up short. Less than 15 percent of calories from fat doesn't provide enough calories or enough fat for other health roles, especially for those involved in endurance sports. Getting enough essential fatty acids is also important for health and peak performance.
Athletes who consume too little fat, often to keep weight and body fat down, may risk a shortfall in food energy; young athletes on a very low-fat diet may not consume enough essential fatty acids for normal growth and development. For female athletes—often dancers, gymnasts, and skaters—a very-low-fat diet may interfere with menstrual cycles, with lifelong health implications.
Do you burn a lot of energy? Since your calorie needs are higher, your total fat intake is probably higher, too. That's often true for football linemen and weight lifters, who may use 4,000 calories or more a day. Still, fats shouldn't contribute more than 35 percent of total energy.
Action plan. Do you need to cut back on fat? If so, get more food energy from carbohydrates. Remember that
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