Exercise is great for every part of you, and it's easy to get hooked once it becomes part of your routine and you start feeling the effects. You may notice your appetite increase as your exercise intensity increases, and that's normal. Nutrition and exercise are very closely connected, and if you don't give your body what it needs, your performance will surely suffer. It's not about special foods or secret formulas -- it's about nourishing your body and feeding it the basic building blocks of energy and strength.
Calories
Calories are a unit of measurement for energy. When you read a nutritional label, the calorie listing refers to the number of energy units that food provides. If you don't eat enough calories, your body begins to feed off your fat stores and muscle tissue to produce the energy it needs, and you'll feel fatigued. You definitely won't perform at your peak. If you take in too many calories, your body will hold on to whatever it doesn't use and store it for a later date, as fat. Ask your doctor or use an online calculator to determine how many calories you need based on your size, age, gender and activity level. Even once you have the calories figured out, it's still a question of where those calories come from.
Carbohydrates
Carbohydrates are your main source of energy. Any plant material you eat contains carbohydrates, which get broken down into glucose during digestion. Your body uses part of the glucose as fuel right away and then converts the leftovers into glycogen for later use. Any glucose that's left over from this process gets converted to fat and stored. When you exercise, the glycogen is what powers the intense activity after your glucose supply runs dry -- in fact, if you are an endurance athlete, your glycogen stores are directly related to your performance. The more glycogen you have stored in your liver and muscles, the longer your energy can sustain your activity. Most athletes do well getting 50 to 60 percent of their calories from carbs, but that figure can easily climb to 70 percent or higher if you're training for a major event like a marathon or triathlon.
Protein
Protein helps the athlete by building and repairing muscle tissue, but not all protein is created equal. Animal proteins contain all of the amino acids necessary to sustain the bodily processes, but plant proteins do not -- they are called incomplete proteins. If you are a vegetarian, you must eat the widest variety of vegetables, whole grains, seeds and legumes as possible to avoid missing out on key amino acids. Divide your weight in pounds by 2.2, and then multiply it by 1.8 to figure out how many grams of protein you need. If you eat enough carbs, all your protein will go toward muscle repair. If you don't, you'll end up burning protein as fuel, which makes endurance activity much harder and less sustainable and can lead to dehydration as water is released.
Fat
Although most athletes strive to maintain the lowest body fat percentage they can, the fat you eat is important. Fat helps your body absorb vitamins, which help your body transport oxygen through the blood, helps keep your cells healthy and participates in a myriad of tiny little functions you take for granted. A 2003 study in "Medicine and Science in Sports and Exercise" found that a high-fat diet didn't negatively affect endurance, but you still don't want to overdo it -- fat has more than twice as many calories per gram than protein or carbs, and extra calories are stored as fat that can slow you down. Get about 20 to 35 percent of your calories from fat, but avoid saturated fat that can affect your cardiovascular performance.
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