Underweight — the other side of the coin

It was Coco Chanel who once said that you can never be too thin or too rich, but she was undoubtedly wrong on at least the first count! The belief that the thinner an individual is, the better, is in fact a dangerous misconception, because research has shown that just as mortality rises along with weight, it also rises with excessive decrease in weight. It is therefore essential to prevent unnecessary weight loss and to be realistic about one's optimal weight for height.

In our society with its ideals of unrealistic thinness, the problem of underweight is often not taken seriously, yet it can cause as much distress as its opposite. The basic cause of underweight is an inadequate energy intake and/or excessive burning up of energy. People who suffer from it are generally very active, tense or nervous get very little rest, smoke, or eat poorly and irregularly. It can of course also affect those whose food intake is low and energy expenditure high due to illness, fever, gastro-intestinal disturbances, cancer or hormonal imbalances.

In recent years, however, there has been an alarming increase in an entirely different cause of excessive thinness, namely self-induced starvation and purging (laxative abuse, vomiting). Otherwise known as anorexia nervosa and bulimia, these serious eating disorders are confined almost exclusively to adolescent girls and young women.

Many researchers maintain that the incidence of eating disorders has increased significantly over the past two decades. Anorexia nervosa used to be a relatively rare condition, but is now said to occur at a rate of one new case per year for every 100-200 middle- and upper-class adolescent and young adult women (between 0,5 and 4% of the population). The incidence of bulimia is estimated to be somewhat higher (5-19%). Anorexia nervosa occurs throughout adolescence and young adulthood with peaks in early adolescence (12-13 year olds) and at about 18 years old. Bulimia sometimes appears as a complication of anorexia nervosa (also called bulimia nervosa) in middle adolescence, or as an isolated phenomenon during adolescence or young adulthood.

Anorexia nervosa

The American Psychiatric Association has defined the following criteria for the diagnosis of anorexia nervosa:

• Refusal to maintain a body weight which is above a minimal normal weight for age and height - for example, weight loss or failure to gain; weight during a period of growth, resulting in a maintained body weight which is 15% below normal.
• Intense fear of gaining weight or becoming fat, even though underweight.
• Disturbances in the way in which one's body weight, size or shape is perceived; for example, the person claims to feel fat even when emaciated or believes that one area of the body is too fat even when obviously underweight.
• In females, absence of at least three consecutive menstural cycles when there is no other underlying cause.

Bulimia nervosa

Criteria for the diagnosis of bulimia have been defined as:

• Recurrent episodes of binge-eating (rapid consumption of a large amount of food in a short period of time).
• A feeling of lack of control over eating behaviour during the eating binges.
• Regular self-induced vomiting, use of laxatives or diuretics, strict dieting or fasting, or vigorous exercise, in order to prevent weight gain.
• A minimum average of two bingeing episodes a week over a period of at least three months.
• Persistent over-concern with body shape.

Secrets of Athletes and weight control

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.