For many sportsmen and -women, there are distinct advantages to maintaining an optimum ratio between body fat and lean body mass. Gymnasts, wrestlers, ballet-dancers and even jockeys strive for a low mass and a high strength-to-mass ratio. Fat tissue does not contribute to the generation of force or power and therefore, must be carried as 'dead' weight in activity involving strength or during any weight- bearing exercise (for example, in a sport like distance running). In fact, leanness is often a good predictor of performance. However, for many athletes, the 'quest for thinness' may become a pre-occupation.
An athlete may try to control body weight in one of several ways. Firstly, he or she may attempt to reduce and maintain a minimal body mass. This is commonly achieved in what amounts to chronic 'undernutrition'- which may in fact result in nutritional deficiencies. It has been shown that it is difficult to take in adequate amounts of certain vitamins and micronutrients - such as B12, folic acid, iron and calcium - when food energy intake is below 5 000 kilojoules (or 1 200 calories) per day.
In addition, chronic low energy (kilojoule) intake in endurance trained athletes will result in certain changes in metabolism, in order to 'spare' energy. An athlete with a low intake may be able to eat less to maintain his or her current body mass, than one with a normal intake. There may be changes in thyroid hormone function, menstrual irregularities in women and a decrease in 'resting metabolism' (see page 128). All these factors point to undernutrition.
Many athletes - particularly young ones - aim to increase their lean body mass or 'muscle bulk', so as to improve performance in some sport. This may involve special diets, protein supplements, drugs to stimulate appetite and anabolic drugs (such as the much-publicised anabolic steroids). A recent study of 76 local resistance-trained athletes revealed that they were taking in nearly 3 times the RDA (recommended dietary allowance) for protein, and then supplementing their diet with protein powders. These sportsmen would be expensive to feed - and, as already shown, their efforts would be to no avail.
It is important for an athlete to recognize that attempts at weight gain in order to increase muscle mass are only effective if accompanied by a resistance training programme which overloads the muscle. In addition, there is no strong scientific argument for supplementing the diet with protein to this extreme, and the long-term consequences on kidney function are as yet, unknown. Drugs, especially anabolic steroids, also have potentially harmful long-term side effects; in addition, they are illegal and generally considered as a 'cheating' method of improving performance.
Finally, many sports involve specific weight categories and certain athletes are regularly involved in 'making weight' prior to competition. Examples of these sporting activities include body building, boxing, martial arts, horse racing and collegiate wrestling. There has been a great deal of research into the weight control practices and dietary patterns of American collegiate wrestlers. In a study of over 700 high school wrestlers, it was estimated that these athletes lost between 2 and 12% of their body mass within 2-48 hours prior to competition. This 'weight cycling' was repeated between 5 and 30 times per season for each wrestler! Sixty-nine college wrestlers were surveyed and results revealed that the average weight a wrestler needed to lose to compete in a specific category was approximately 4,5 kg, 3 days prior to competition. All of those surveyed gained weight in the off-season, and tended to flucuate between 5 and 9 kg above competition weight each week during the season!
The rapid weight losses achieved by these athletes usually involve cutting down severely on food and fluid intake and 'thermal' methods designed to lose water through sweating (plastic suits, saunas, etc.). But studies show that this can be counterproductive, since a loss of as little as 2% of total body weight through dehydration causes reduced exercise and heat tolerance, which in turn may result in poor performance.
There is also evidence that athletes who regularly undergo 'weight cycling' or 'yo-yo' dieting and weight loss may experience long-term changes in growth and metabolism. Wrestlers who constantly have to 'cut weight' in order to compete have been shown to have a slower metabolic rate than those who can compete without losing mass. So, while leanness may be a good indicator of performance in some sports, the 'quest for thinness' itself may have a detrimental effect. Manipulating body weight through weight 'cycling' may also result in long-term changes in metabolism; the athlete should rather strive for a balance in weight control which will improve his or her performance in the long-term.
It is unlikely that manipulating food intake or a single isolated nutrient will lead to enhanced performance on its own. An overwhelming number of studies have shown that supplementing a balanced diet, containing sufficient protein, vitamins and minerals has no benefit on athletic performance. A consistent and well planned training programme is still the most effective way of improving athletic performance. However, good nutrition supports the training programme in ensuring optimal performance, and sound nutritional practices will allow the athlete to achieve his or her potential.
