FAT LOSS: FIXED FACTORS
Gender. There are major differences between males and females in fat loss responses to exercise. Female fat cells are predominantly less lipolytic than those stored around the abdomen of males, and are hence less responsive to exercise. Most researchers now agree that this has a biological function in providing females with an energy reserve for reproduction. There is some suggestion that female gluteal-type fat cells may even be resistant to some types of activity, such as high intensity exercise in younger, pre-menopausal women. Studies carried out at McMaster University in Canada have also shown that, unlike males, female athletes seem to be less effective in ‘carbohydrate loading’ for long endurance events such as the marathon.4 (Carbohydrate loading is a technique whereby large amounts of carbohydrate are eaten 3-4 days before an event in order to ‘fill’ the glycogen reserves which supply immediate energy for the event. This ’suggests the capacity for glycogen storage is decreased in females and they prefer to use carbohydrate for immediate energy rather than storage.)
Differences in the hormonal environment and body composition lead to a greater fat loss response to a set exercise load in men, and a guaranteed response to almost any form of exercise in younger men. Biomechanical differences and the higher proportion of body fat in women make them more efficient at some forms of exercise, thus using significantly less energy than men for a set exercise stimulus. It has been estimated, for example, that an average-sized woman will use approximately 40 per cent less energy than an averaged-sized man in walking an equivalent distance. Swimming involves an even greater energy differential between genders because of the higher proportion of body fat and the lower centre of gravity in females (enabling them to float more effectively and maintain a more efficient body position). Research at Leeds University in England suggests that females may also eat more after exercise than men, thus making up for the extra energy used during the activity.
All of this has led Dr Gilbert Gleim, a US exercise scientist, to conclude that: . . As an isolated weight loss modality . . . Exercise should not be counted on to produce desired weight reductions (in women) unless the woman is committed to many hours of exercise a day’.
Exercise prescriptions then need to take account of the greater lipolytic resistance which occurs with reduced energy balance, greater compensatory eating and the reduced muscular response
To resistance training. All of this suggests a need for a significantly greater total amount of exercise in females in order to achieve the same fat loss benefits from exercise as a man. On the more positive side, any amount of exercise in women (as well as men) has been shown to improve health profiles such as blood pressure, cholesterol, blood sugars and feelings of well being, even if it doesn’t have a major impact on body fat. Older females, with a higher proportion of upper body fat, might be expected to respond more like a man, at least in the reduction of their upper body fat to a given exercise load.
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