Health: Sex and weight loss

Gender counts in the post-Christmas battle of the bulge

Just like everyone else, cyclists have been known to gain a bit of weight over Christmas or after a non-cycling holiday. Eating good food is one of the pleasures of life and, after all, exercise is the best way to counteract any excesses.

The road to the perfect diet and fitness programme is littered with myths, misconceptions, discarded trends and mixed messages. So, is it true that exercising on an empty stomach burns more fat? And why do men come back from two weeks of cycle touring having shed pounds when women do the same distance but their weight doesn't budge? 

There is a lot that we still don't understand about weight management. One thing that is clear is that most men tend to lose weight more easily than most women. Men simply add on exercise, subtract the extra beer, crisps, chocolate and fatty foods, and the extra pounds melt away. Women by comparison complain that they lose a bit of weight, reach a plateau and cannot seem to shift the last few pounds despite regular bike rides.

The reasons for this are complex but include the effect of exercise on appetite and nature's design of the female body. The latter relates to the women's need to maintain a supply of calories to support a nine-month pregnancy. 

This is nature's way of ensuring survival of the species, but not much help when your priority is fitness and weight loss rather than producing more young cyclists. Exercise may temporarily dampen your appetite, but hunger usually kicks in after an hour or so.

Exercise and appetite

Exercise on its own is not an effective way for women to lose weight. Appetite is partially regulated by body temperature so if you are hot and sweaty after a long ride or training session, you may not feel hungry for a while. But a tough cycle in rain or a cold wind may leave you feeling ravenous. 

This effect of exercise on appetite seems to be different in men and women. Controlled experiments using rats showed that male rats who exercised regularly ate less and lost weight. In comparison, the female rats after exercise seemed to have a lively appetite which stimulated them to eat more and maintain their weight.

Another study, using human volunteers, showed that even without an increase in appetite, men still seem to lose weight more easily compared with women. A group of normal weight but unfit men and women took part in an 18-month training programme (to prepare them to jog and complete a marathon event). 

The men increased their daily intake by 500 calories while the women limited theirs to an extra 60 calories per day. Both groups were running 50 miles per week. The men lost about 5lb of fat, the women lost none.

Fat and fertile

Other studies have also shown that exercise, on its own, is not an effective way for women to lose weight. Lean female athletes in particular tend to struggle to lose fat. It is clear that evolution has hung on to the design to ensure that women are fat and fertile while men are more useful as lean hunters. 

When food was scarce or fluctuated because of a poor harvest or the effects of the seasons, women developed a mechanism of energy expenditure which is very efficient. As each cycle of famine followed by a feast came round, women became more efficient at storing any available energy as fat and developing a mechanism which would not give it up easily. This allowed women to survive and to conserve essential fat stores to support the next pregnancy.

These days the cycle of famine and feasting is known as 'yo-yo dieting'. The belief that more fat will be burned on an empty stomach has some truth. Before breakfast, your blood sugar and insulin levels will be low. This will stimulate release of fat to be used as fuel during exercise. However, it is the total calorie balance at the end of the day which counts, in terms of weight loss, not just what you burned during exercise.

Life balance

After a long ride, you may feel hungry but also tired. It's easy to confuse tiredness with hunger (especially when you are trying to limit your calorie intake). So it's easy to overeat (especially at night) when you feel tired, or you simply want to enjoy a good meal as a reward for all that exercise you've just done.

Life is all about balance. It is important to balance the enjoyment of eating with that of cycling. If you ride just to burn off the calories, exercise then becomes a punishment. Change your eating habits to lose weight but also change your attitude. Enjoy cycling for the long term health benefits, not just to support a short term diet

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