STUDY ANALYSIS: Actually, Exercise Does Have Different Effects on Women and Men

An interesting new study gives credence to a social-media chestnut

I’ve seen it a lot on social media and so have you, I’m sure. A woman pleading that exercise and weight-loss strategies don’t work the same for women as they do for men. Sometimes you’ll also get a stronger claim about the gendered nature of science to go along with it: science is gendered, with the majority of research into physiology, and especially exercise physiology, being carried out on men, not women. Ergo, little to none of it is directly relevant to women.

There’s clearly something to this, on the face of things. Women and men really are different, not least of all in things like body composition and especially hormones. How far we should take the argument—and whether we need a totally female-focused science to understand the effects of, say, resistance training on women—remains to be seen, however.

Anyway, there was a new study released in May that sheds an interesting light on this issue. According to this new study, male and female rats are programmed to burn fat differently, which may explain why actually women don’t benefit from exercise in quite the same way as men.

The researchers found that there were significant differences even in sedentary male and female rats, but those differences were supercharged, as it were, when the rodents starting exercising.

“We found that fat tissue between males and females is very different even in sedentary animals,” explains Christopher Newgard, a study author and director of the Duke Molecular Physiology Institute.

“But then I was truly gobsmacked with how amazingly different the sex-dependent responses to exercise are. Males burn fat for energy while females preserve their fat mass. This is brought about by many differences in molecular responses lurking beneath the surface in fat from male compared to female rats. The dichotomy is truly striking.”

The researchers took tissue and blood samples from rats that ran on treadmills over a period of eight weeks. They measured concentrations of thousands of different kinds of proteins to gain an idea of the effects of exercise on metabolism and fat-usage and on white fat, in particular. White fat is less metabolically active than brown fat, which plays an important role in thermoregulation and metabolism.

With regard to sedentary male and female rats, it was clear that there are already massive differences in metabolism, as revealed by analysis of proteins. More than 20,000 molecular measures differed between them.

Clearly, there are substantial baseline differences between male and female rats. Exercise only enhanced these differences.