09/20/2012 08:03 am ET Updated Nov 20, 2012

If Carbs Are So Bad for You, Why Are They So Good for Athletes?

Anyone watching the Olympics, professional baseball or training for football season over the past several weeks has to conclude that the athlete's bodies and ours could not belong to the same species. As I watched the swimming relays, it was hard to believe that my plodding crawl, accompanied by gasps of breath, and the athletes' seal-like fluidity are both called swimming. It was also a stretch to say that their running leaps over the hurdles were at all related to my occasional clumsy climb over a low fence. But as different as they seem from us, their bodies and ours share a common need for nutrients to make our muscles move, however fast or slow that may be.

Carbohydrates have long been considered the most important source of energy for any type of muscle activity, be it leaping over a hurdle or climbing out of bed. However, given the seemingly endless anti-carbohydrate hype, I wondered if carbohydrates have now been eliminated from the diets consumed by athletes. Fortunately for those among us who still are eating our "daily bread," pasta, rice, potatoes and oatmeal, sports nutrition folk still recommend carbohydrates for the competitive athlete -- and also for anyone engaging in more than 10 milliseconds of physical activity.

Glucose is the form of carbohydrate used by our muscles for energy. A simple sugar, glucose is the digestion end product of all carbohydrates, whether they are sweet or starchy. Glucose is stored in muscles in the form of glycogen and converted back to glucose during exercise. When swimmers or runners manage to cover the required distance in only a few minutes, the stored glucose in their muscles is sufficient to deal with their energy needs. Indeed, it is believed that muscles contain enough glycogen to carry us through exercise lasting around 90 minutes. (That is, of course, assuming we eat carbohydrates).

But many competitive athletic recreational events take longer than an hour and half. Biking for several hours to cover a 100-mile charity ride, or spending most of the day cross-country skiing, increases the need of the muscles for glucose. According to researchers, J. Anderson, L. Young and S. Prior at the University of Colorado, the preferred method of ensuring a continuous supply of glucose is to eat a high-carbohydrate diet two or three days before the event. This allows the extra glucose in such a diet to be stored in the muscles so it can be used for prolonged exercise such as a marathon.

Fats, or to be more exact fatty acids (they make up half of a fat molecule), may also be used by the body for energy. Although this sounds like the perfect solution for exercising on a low- carbohydrate diet, eating fats work best for the well-conditioned, well-trained, undoubtedly lean athlete. For the rest of us who are not quite Olympian level in our workouts, using fat as an energy source is relatively inefficient. The problem is not with our fat stores, since most of us have more than enough to provide our muscles with energy for a 100-mile ride. But converting the fat, or specifically the fatty acids, to a usable form of energy requires much more oxygen than converting glucose to energy. So if you are huffing and puffing while climbing a steep flight of stairs, lifting heavy groceries or finishing a dance aerobic class, it is going to take more huffs and puffs to get energy from fat than from glucose. And when your muscles run out of energy, your workout may come to a premature end. Interestingly, athletes competing in endurance sports like a triathlon are told to replenish their carbohydrate stores with either drinks containing carbohydrate or rapidly digested energy gels containing glucose. No one in the articles I have read suggested eating a chunk of butter for more energy during a long run.

Protein is essential for muscle growth. No amount of strength training is going to result in enlarged muscles unless the diet contains adequate amino acids to make muscle protein. The consensus among sports nutrition folk, such as Nancy Clark, RD, is that our diets contain enough protein to meet the needs of our enlarging muscle. But you don't have to go to a health food store to read the label on a jar of protein power to figure out how much protein you need. This is how you do it. Figure out:

  1. Your ideal body weight (not what you presently weigh, if there is a difference);
  2. Convert your ideal weight in pounds to kilograms by dividing your weight by 2.2; and
  3. Multiple your weight in kilograms by 0.8. This tells you how much protein you should be eating daily.

Is this enough protein for you if you are an athlete? Maybe not. Weight lifters may need as much as 1.6-1.7 grams of protein for each kilogram of body weight. Lifting your toddler or grocery bags does not count. Are you training for a long run or bike ride? Endurance athletes may also need more protein, approximately 1.2 to 1.4 grams per kilogram body weight.

But for the rest of us, more is not necessary. Extra protein is converted to fat and most of us have enough, thank you.

But what about protein as an energy source? It ranks third after carbohydrate and fat. Should you be lost in the wilderness with no food, your body will look to your stored glycogen for energy first, then your fat stores and eventually the protein in your muscles. But for those of us who are only lost in the wilderness of a parking lot trying to find our car, we are unlikely to call upon our protein stores to get to our vehicle.

If you have been feeling guilty about eating carbohydrates, or attempting to fight off advice about giving them up, look toward our athletes as justification for doing so. However, there is no "free lunch." Your body will store them for you as an energy source but it is up to you to use them for that purpose.

For more by Judith J. Wurtman, Ph.D, click here.

For more on diet and nutrition, click here.


University of Colorado and USDA extension program pamphlet, 12/96