A little bit of dessert in moderation is fine, of course, but don't overdo it. If you find that you have a nagging sweet tooth, your body may be trying to tell you that you need more calories. Rather than indulging in a candy bar, you might do better to eat a bit more at meals or add a healthy snack in the afternoon (fruit, cereal or a sports bar).
Trim the fat
If most people need more carbohydrates, it's also true that most should cut back on fat. Not that fat is all bad. It's a necessary part of the diet, offering up both energy and flavor. Still, most of us eat too much of it. Fat should account for only 20 or 25 percent of caloric intake (the average American hovers around 35 percent). While everyone deserves a treat once in a while, try to avoid fatty foods like whole milk, red meat, ice cream, mayonnaise, egg yolks, chocolate, butter and cheese.
Some fats, however, can actually do you some good (though all are chock full of calories). These are the unsaturated fats, particularly monounsturated fats like those in olive oil, peanut oil and avocado oil. Unsaturated fats can actually reduce blood cholesterol. While margarine is made of unsaturated fats, it is also hydrogenated which negates the cholesterol-reducing benefits. Healthwise, there's not much difference between margarine and butter; neither is particularly healthy, and both should be used sparingly (when push comes to shove, tub margarine may be your best bet for reducing cholesterol).
When it comes to fat, the real bad guys are the saturated fats. These come primarily from animal sources such as red meat and milk, but also from coconut, palm and vegetable oils. They are closely linked with heart disease, obesity, diabetes and some cancers. Try to keep saturated fat down below 10 percent of your total calories, or around a third of your total fat intake.
Protein: Beware too much of a good thing
Your protein intake should be a bit lower, at 10 to 15 percent of total calories. This may seem odd, since many of us grew up on the myth that high-protein diets were the essential building blocks for any athlete. In fact, your body stores excessive protein as fat. If you really overdo it, by taking too many protein supplements for example, you could even damage your liver or kidneys. All of which is simply to say beware too much of a good thing. And proteins are, after all, a good thing. They help bone and tissue to grow and repair, and they're the stuff that blood, skin, hair, nails and organs are made of. Proteins are literally body builders, and it's important to get a sufficient amount.
In fact, since you burn some protein as fuel when you exercise, runners need a bit more protein than non-runners. Endurance athletes, for example, average one and a half to two times the RDA for protein. A good rule of thumb is to eat about half a gram of protein daily per pound of body weight. Good sources of protein are fish, lean meat, poultry, beans, nuts, whole grains, egg whites, low-fat milk, low-fat cheese and some vegetables.
Vegetarians, in particular, should be careful to get enough protein. While study after study has demonstrated that a vegetarian diet promotes health, it must be carefully planned to compensate for the nutrients you would otherwise get from animal sources. For some athletes, fatigue and poor performance have been a result of switching too carelessly to a vegetarian diet. In addition to stocking up on proteins (with cereals, whole grains, legumes, and nuts for example), vegetarians should also seek alternative sources for iron and zinc.
The big picture
In the end, a good diet is a lot like a good training program. Over the long haul, a sound nutritional routine will deliver strong results and increased performance, in the same way that a balanced workout program gradually improves your conditioning. Since both are much more important over the long run than in the short, your diet, like your training program, should be viewed in the big picture. It's difficult to derail yourself nutritionally over the short term. A few days of epicurial indulgence will not ruin your racing form any more than taking a few days off from your training routine. Don't be anxious about the day-to-day. Always keep the big picture in mind.