Gender and fat loss
By Professor Steve Boucher
Overview: There are many reported anecdotes of husbands and wives going on an exercise program together and the husband losing significantly more weight than the wife. But does research support the notion that men and women’s body fat responds to exercise differently? If so, are there gender-based mechanisms to explain why women are different from men? This is important to establish because if women have greater trouble losing fat they are likely to need female-specific fat loss programs.
Do women lose less fat after exercise compared to men?: There is surprisingly little research into this topic. However, some well controlled studies have shown that women do lose significantly less fat when engaging in exercise-based fat loss programs compared to males. For example, Donnelly et al. (2002) carried out a 16-month exercise intervention in overweight males and females aged 17-30 years. They found that the men lost on average 5.2 kg of weight compared to no decrease in the women. A small number of other studies have reported similar findings. Mechanisms underlying gender differences are complex and include the following: differences in body fat distribution, smaller energy expenditure of exercise, greater energy intake, fat oxidation patterns, and societal forces.
Gender differences in body fat distribution: Females have a gynoid whereas males typically have a android fat distribution. Thus, females have fat stores on their hips, legs, and upper arms, whereas males concentrate their fat around their abdomen. Fat content for men is about 12-24% and for women about 15-35%. Women need to store extra fat to help with pregnancy. Female fat stores are generally in smaller fat cells around the hips. In contrast, men have larger fat cells around their abdomen.
Energy expenditure of exercise and compensatory intake: There is some evidence to suggest that compared to men, women have a smaller energy expenditure to exercise. Because women typically have less muscle than men the energy used up in exercise is significantly less for women of the same weight. Also research has shown that some women tend to increase their energy intake (eat more) after exercise more so than men. Other research has shown that men generally put on weight through ignorance of basic nutrition, whereas women tend to put on weight more because they use food as a strategy to cope with life’s stressors. Cortisol is a major stress hormone and has been shown to induce the body to store rather than burn fat. So gender difference in cortisol levels may have an influence.
Fat oxidation patterns: It also appears that for the same amount of physical effort women burn less fat than men. Gender difference in fat utilization, however, is a controversial area. Other hormonal gender differences may involve thyroid. Low thyroid activity is a major impediment to fat loss and Australian women have more thyroid problems than men.
Summary: It seems that men can perform more vigorous exercise which may be more conducive in reducing abdominal fat. Women are disadvantaged by their smaller muscle mass and larger fat mass. Also women, generally, may possess greater problems with a sluggish thyroid gland. Recently, we have shown that women can lose significant amount of fat using intermittent sprinting exercise. Thus, the 8/12 second lifesprint protocol may be powerful enough to induce significant fat loss in women.
*for the reference mentioned above see:
Donnelly et al. (2003). Effects of a 16-month randomized controlled exercise trail on body weight and composition in young, overweight, men and women. Archives of Internal Medicine, 163, 1343- 1350.