To be fast you must be lean. Cheetahs, the fastest animals on earth, can reach speeds of 70 M.P.H. But only because they are very lean. The same principle applies to humans. It’s easy to observe that the athletes winning the races are very lean.

In general, for given muscle power and leg speed, the lighter the load, the faster the speed. Athletes with a higher percentage of body fat will run slower than they could run if they were leaner. But how does one become leaner?

There are many different opinions on this subject, some not helpful, some even dangerous. The following review of a few food facts and new research reveals sensible, safe ways for an athlete to become leaner and stronger.

First, some basic food facts:

There are three basic food groups:

1) Proteins build muscles, organs, bones, enzymes, immune cells and many hormones.

2) Carbohydrates are fuel for immediate use.

3) Fats provide insulation, cushioning and calorie storage and help build cell membranes and some hormones.

All foods can be converted to fat if you eat too much of them. Excess carbohydrates, proteins and fats will make you fat. A little known fact is that most of the proteins that we eat are turned into carbohydrates and used for fuel or stored as fat. For example, 83% of any whey and soy proteins that are eaten are not used to build body protein, but as carbohydrates.

Here’s why:

The protein in food is made up of amino acids strung together like beads on a chain. When a protein food source is digested, the amino acids are released and absorbed in the small intestine. Some of these amino acids can then be used as building blocks that are recombined to build the required proteins for the body. Only amino acids that are available in the correct proportions can be used to build body protein.

How much of the protein that is digested and absorbed is used to build body proteins?

That depends on the source of the protein. Most people think that if they eat 30 grams of protein that all of those 30 grams will be used by their body to form new proteins or to replace the proteins that are naturally lost each day. This isn’t actually what happens.

Each protein source is made up of different amounts of individual amino acids. Each protein source has a different percentage of its amino acids that can be used to build body protein.

A chicken breast (raw, boneless and skinless) is about 23 percent protein. Therefore 3 oz (85 g) of chicken breast would contain about 19.5 grams of protein. (In a healthy individual, about 2-8% of the protein is indigestible, leaving at least 18 grams of digestible protein.) What is important to realize is that of this 18 grams, only about 30% of it (about 5 grams) is actually “used” by our body to make or synthesize new proteins. The rest (about 13 grams) is broken down and becomes a source of calories.

If you examine whey protein, only 16% of the amino acids are used to build proteins in the body. Therefore 84% of the amino acids are not used to build protein and just become a source of extra calories!

Also it is important to understand that if the amino acids in a protein source or an amino acid formula are not used, in addition to releasing calories, harmful nitrogen waste is released which must be eliminated by the body. (Excess nitrogen waste can stress the liver and kidneys, especially as we age.)

Although all of the food groups (fat, protein and carbohydrates) can be used as an energy source, only protein can provide the essential amino acids required to build body protein. (Carbohydrates are the preferred source of energy for the body.)

So how do you get a lean body?

First. Use carbohydrates prudently. Except during heavy training, avoid products containing high fructose corn syrup. Instead of consuming sports bars and drinks with high fructose corn syrup, eat natural and unprocessed foods, including fruits and starchy vegetables.

Second. Avoid all refined grains (white flour, white rice and most baked goods). They are poor food sources for everyone.

Third. A void most processed foods and “fast” foods. Read food labels. If additives, preservatives, colorants, chemicals, flavorings, seasonings, etc., are listed, pass them by.

Fourth. A void all foods with trans fats, deep fried foods and margarine.

In general, eat mostly healthy, natural, unprocessed foods: fruits, vegetables, fish, nuts, non-processed meats, beans, and eggs. Eat like our cave man ancestors. (Eliminate sugar and processed foods.)