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Nutrition For Fitness and Health

Updated on September 8, 2011


To improve fitness and/or strength, two things are necessary; the right sort of exercise for your chosen goals, and the right sort of nutrition. The requirements for both are different depending on whether you are primarily aiming for fitness or for strength and muscle size, as can be readily seen in the difference between the exercise regimes for a long-distance runner and a weightlifter.

It is also true that there is a genetic bias in each person. People who make good marathon runners would never make good weightlifters, and vice versa; but in this article I am assuming that you already know what sort of athletic endeavour you are going to be best at.

This article does not give advice, in any but the most general terms, about how to do the exercise to attain your fitness goals. The reason is very simply that I do not know very much about that subject, and it would undoubtedly be better if you got your advice about exercise programmes from someone who does – perhaps elsewhere on this site?

The subject of nutrition can, and probably should, be split into the subjects of general diet and supplements. It is the opinion of most experts on this subject that, although one can get a long way by eating the right foods, the last few percent of ability (which often makes the difference between winners and losers) can only be achieved by using the right supplements as well.

Diet for Fitness

The main principles of correct diet for someone interested in fitness start with advice that could be given to just about anyone; avoid junk food. To clarify this, junk food in this context (at least, probably in many others as well) includes foods with lots of sugars and other refined carbohydrates such as white bread and white rice, any foods with large amounts of unnatural chemicals such as preservatives and artificial colours, fried food and foods containing hydrogenated or trans-fats.

It is probably worthwhile digressing about trans-fats. Fats can be split into two or three categories; saturated and unsaturated – the latter can be split again into monounsaturated and polyunsaturated fats. Saturated fats are primarily found in animal fats, but also in palm oil; monounsaturated fats in olive and peanut oils; and polyunsaturated in more or less all other plant oils and also in fish oils. The term “unsaturated” here refers to details of the chemical structure of the fat; specifically, an unsaturated fat is one where there are less hydrogen atoms in the molecule than could be the case. This lack of some hydrogen atoms leads to specific things about the shape of the molecule, and also unsaturated fats have specific biological functions that saturated fats cannot fulfil.

Regarding trans fats; the lack of hydrogen atoms in an unsaturated fat leads to one or more double bonds in the molecular chain. For reasons buried in quantum mechanics, this leads to the section with a double bond having a specific (flat) shape. This shape comes in two forms, cis and trans, that require a great deal of energy (usually heat) to flip one to the other. The form usually found in natural fats is the cis form; unfortunately, the trans form is more stable.

Unsaturated fats are more susceptible than saturated ones to various forms of damage such as oxidation (rancidity) and various other forms of free radical attack. Unfortunately, although trans fats are just as susceptible to such damage as cis form fats (the natural sort) they are completely useless for the various specific things the body does with unsaturated fats – so they have all the disadvantages and none of the advantages of natural unsaturated fats.

Fried food, especially fried in unsaturated oil (which is nowadays the norm), contains relatively large amounts of unnatural chemicals such as acrylamide, found in fairly large amounts in fried potatoes; the probable source of this is reactions between starch and some of the protein in the potatoes. Acrylamide is a carcinogen more usually used in the manufacture of various plastics and commercial paints. Although the amount found in fries is not immediately toxic, it ought to be obvious that eating the stuff is hardly going to be good for you. Food fried in unsaturated oils will also contain trans-fats in large amounts.

For these and many other reasons, therefore, it is essential to have a generally healthy diet if you expect to be fit. However, the diet for someone burning a lot of calories, as someone training for fitness and/or strength should be, is slightly different from a generally healthy diet. Specifically, the diet for fitness training ought to be about 70% complex carbohydrates (from potatoes, vegetables, fruit and whole grains), 20-25% protein and 5-10% essential fatty acids from fish, nuts, seeds and various other vegetable oils. Despite tradition to the contrary, red meat with its associated saturated fat is not necessary for health or fitness.

These dietary suggestions may be counter-intuitive; many people think that large amounts of extra protein are necessary, particularly for strength training. But this is not actually the case. The reason is that the actual amount of protein that can be used for muscle building is rather small. What is important is to make as sure as possible that the protein being ingested is used to build muscle rather than for energy, which means plenty of carbohydrates in the diet. The body and particularly the muscles can use protein for energy, but this is massively inefficient; digesting and breaking down large amounts of protein for energy put a heavy strain on the digestive system, liver and kidneys.

Vegetables, whole grains and fruit supply, as well as the carbohydrates and protein, other things as well; in particular, a selection of vitamins and minerals and also fibre, which keeps the digestive system in order.

Supplements for Fitness

I will set out the supplement requirements for fitness training in order of importance, most to least important.

Vitamins, Minerals and Vitamin C

Enzymes in the body are responsible for initiating all the reactions that constitute the metabolism; a perhaps over-used analogy is that enzymes work a little like the ignition system of a gasoline engine. Enzymes are composed of protein, almost always incorporating one or more molecules of vitamins or minerals or both. Therefore, lack of sufficient amounts of vitamins and minerals means that the metabolism is going to go wrong or be less efficient in one way or another.

While it is possible that a generally healthy diet may provide enough of these nutrients for general health in someone who has an average lifestyle, it is much less certain that such a diet is good enough for someone who is asking as much of his or her body as is someone in serious physical training, so it’s a good idea to take a high-quality multivitamin/mineral each day. In addition, there is a real question about vitamin C in particular.

Vitamin C is not a vitamin at all for most of the animal kingdom; for example, cats and dogs don’t need it in their diet. The production of vitamin C in an animal body is a fairly simple process involving four enzyme-catalysed steps; one of the four is L-gulonolactone oxidase, and that is the enzyme that humans happen to lack because of a mutation that is thought to have occurred about 25 million years ago in one of our ancestors. In any case, this is the reason why humans require vitamin C.

Vitamin C is consumed, in quantities 10-20 times higher than the official RDA for people, by our closest relatives such as gorillas and chimpanzees. Most other animals of our approximate size make considerably more than that for their own use. It seems, therefore, at least arguable that people really need 1000-2000mg for optimum health, which won’t fit into a multivitamin; so adding extra vitamin C to the list is necessary for optimum results from an exercise programme. This is particularly important because one of the major functions of vitamin C is in tissue building.

Digestive Enzymes

The requirements of the body during intense physical activity are greatly increased. This is particularly so for strength training, because muscle building requires extra protein and protein is probably the most difficult component of food to digest. Because of this, it is sometimes necessary to supplement the body’s natural digestive enzymes. Supplements of digestive enzymes are widely available.

Anti-Catabolic Agents

This section requires some explanation. The body always has two opposing processes going on, called anabolism and catabolism. These mean building and breaking down of tissue respectively, and the reason why both processes continue throughout life is simply that cells wear out. The rate at which this occurs depends on the tissue in question; the extremes are the bones (about a 10-year turnover time) and the lining of the intestines, whose turnover time is measurable in weeks. Even nervous system tissue such as the brain turns over, although in this case the repair and replacement are within the cells.

To build muscle, the balance has to be moved towards favouring the anabolic process; to keep the muscle you already have, what is needed is to keep the balance rather than favouring catabolism. Excessive catabolism can be an issue if you are training hard and not replacing the needed protein.

There are several ways to suppress catabolism. One is simply to keep adequate levels of fuel available, which usually means plenty of carbohydrates for your muscles to burn. But there are two other nutrients that also help. Branched-chain amino acids (there are three of them called leucine, isoleucine and valine), which are often abbreviated to BCAAs, and also L-glutamine are present in large amounts in the major muscle proteins and also serve as fuel for those same muscles when the carbohydrates start running out; it is also true that some of these amino acids are burned as fuel no matter what. Therefore it’s a good idea to supplement with both these nutrients before and after a workout to reduce the muscle breakdown during exercise. It’s worth mentioning that studies have shown it’s possible to “repair” the muscle breakdown after exercise, as long as the material to do it is supplied very soon after the workout – no more than an hour. This means it’s a good idea to supplement protein, if you are going to, after a workout.

Anabolic Agents

The word “anabolic” has had a bad press for the last few years, because of its connection with drugs that are either illegal or against athletic association rules or both. But in fact there are several types of perfectly natural substances that have anabolic effects. One is the pair of arginine and ornithine, often found together in supplements. These increase growth hormone levels if taken late at night, and have also been recently been found to increase blood flow to the muscles (by increasing levels of nitric oxide in the blood vessel walls) if taken before workouts.

Another is the mineral chromium. Chromium works with insulin to control blood sugar levels and get sugar into the tissues as fuel. Also, because of this connection it has mild anabolic effects. Insulin is the most powerful anabolic agent known, bar none, but is also the most dangerous if used from an external source. However, improving the effects of insulin naturally helps to build tissue. The best sources of chromium are chromium picolinate and polynicotinate; only the former is available in the UK for some unknown reason.


Creatine is present naturally in the muscle tissue of all animals, but has only become available as a supplement in the last ten years or so. Its function in the body is to act as a very short-term “energy battery” inside the muscles during intense work such as is done while lifting weights or sprinting. It does this in the following way: Creatine is converted into creatine phosphate, which is a very high-energy compound and is capable of converting adenosine diphosphate (ADP) into adenosine triphosphate (ATP) very quickly. The creatine phosphate is converted into creatine in the process, and this can be reversed during brief rest periods such as the minute or so between “reps”. The reason why all this matters is that ATP is the energy currency of the entire body; all the reactions in the body, including those involved in muscle contraction, are powered by ATP.

Creatine supplementation increases the level of stored creatine, and thus the available energy storage, beyond normal. Thus, creatine improves performance in sports that involve very intense bursts of activity. Its usefulness for more long-duration exercise, such as long-distance running, is more limited; especially because as a side issue the creatine pulls large amounts of water into the muscles with it, which increases the mass those muscles have to move.


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