Three New Findings About Women and Exercise

We know diet and exercise play significant roles in our overall health—yet there’s no one-size-fits-all solution for everyone. And ongoing scientific research suggests that the way females respond to exercise may differ from males. That’s because male physiology is different from female physiology. Yet until recently, most studies “just lumped males and females together and assumed that the response would be the same,” says Dr. Michaela Devries-Aboud, an exercise physiologist at the University of Waterloo, whose research focuses on sex-based differences in physical activity response.

Historically, women have been understudied by exercise researchers. Numerous factors have contributed, including the fact that women’s menstrual cycles create hormone fluctuations in their bodies, which makes some research more complex. “When we do physiological research, we want to keep everything except for the intervention as consistent as possible,” says Dr. Devries-Aboud. “However, what we weren’t realizing is that because of those fluctuating hormones, women may not respond in the same way to a given intervention as men do.”

So what do we know about how exercise and diet affect women’s bodies—and what implications does that have for the way females approach fitness?

1. It may take longer for exercise to improve insulin sensitivity levels in women.

Insulin is created by an organ called the pancreas to regulate the amount of glucose in the blood. You want your cells to be sensitive to insulin levels, so that the body can properly regulate the amount of energy it’s creating. (Insulin resistance, in turn, can lead to all sorts of health problems, including Type 2 Diabetes.) Exercise has long been thought to be among the most effective ways to boost insulin sensitivity. However, developing research suggests that women may not respond as readily to exercise training to improve their insulin sensitivity, compared to men. At this point, we don’t know why that it is. The reason may be that “women are inherently more insulin sensitive than men,” and that estrogen may play a role in all of this.

The greater point? Exercise remains great for women for all sorts of reasons, says Dr. Devries-Aboud. She points out that risk of Type 2 Diabetes decreases in women with increasing amounts of exercise. If you’re a woman who has started exercising because you’re trying to boost your insulin sensitivity, perhaps because a doctor has told you that you’re at risk for diabetes—don’t get frustrated if you’re not yet seeing results. “If you don’t see the improvement right away, it will come,” says Dr. Devries-Aboud. “And just think of all the other benefits you’re getting because you’re exercising more.”

2. Protein consumption may be even more important for women, compared to men, when they’re seeking to protect muscle mass during weight loss.

When it comes to weight loss, the ideal is to lose fat while holding onto muscle mass as much as possible. Fat tissue, after all, can lead to all sorts of health problems, while muscle tissue is necessary for strength, and numerous other wellness-promoting processes. Trouble is, this ideal may be more difficult for women compared to men. One 2018 research trial put 2,500 overweight men and women on an 810-calorie per day diet and looked at the changes in their body composition over an eight-week period. Overall, 25% of the weight loss was lean mass—muscle, in other words. But when you analyzed the results by the sex of the subjects, the women lost twice as much muscle compared to the men. Women’s weight loss was 31% muscle, while male’s weight loss was only 16% muscle.

The implication? To protect that muscle and minimize how much they lose during weight loss, women may want to pay even more attention, relative to men, to their protein consumption, according to Dr. Devries-Aboud. “Higher protein diets during energy restriction are better at helping to preserve muscle mass,” she says.

That doesn’t necessarily mean increasing the amount of protein you’re consuming, says Dr. Devries-Aboud, because most people’s regular diets include the ideal amount of protein. Instead, when you’re looking to lose weight, try to eliminate calories from fats and carbohydrates, while keeping your protein consumption at a consistent level.

3. Carb-loading may not be effective for female endurance athletes.

It is a tradition for athletes in certain endurance sports, such as running, to engage in pre-race carb-loading to provide their muscles with enough fuel to power them through to the finish line. But Dr. Devries-Aboud says the strategy likely doesn’t make sense for most female endurance athletes. “There’s been a few studies that have come out showing that women do not respond to carbohydrate loading like men do,” she notes.

The reason has to do with the absolute amount of carbohydrate that has to be consumed to make a difference. “Generally speaking,” says Dr. Devries-Aboud, “for people to carbohydrate load, they need to consume at least eight grams per kilogram of body weight per day during the loading period.” Men, she says, are able to achieve that amount by altering their diet so carbs comprise about 75% of their energy intake. Women who want to achieve that eight-gram baseline would need to either alter their diet so that it’s all carbs, or increase their energy intake by about 30%, according to Devries-Aboud. “And if you’re doing that in the days leading up to a marathon, all of a sudden, you’re carrying more weight around with you.” Consequently, the University of Waterloo physiologist says, female endurance athletes who believe additional weight may hinder performance may want to stay away from carb-loading. “Any sport where you’re carrying your weight,” she says. “It’s probably not going to help you out.”

There’s no one-size-fits-all solution for everyone when it comes to diet and exercise. The best strategy is to pursue exercise and diet regimens that you can live with over the long-term, to maintain your wellness over your lifespan. Optimizing these strategies for women will require a lot more scientific research on female exercise response. According to Dr. Devries-Aboud, numerous studies are happening at universities across the world, and we should know more soon. She says, “I think the future is bright when it comes to understanding the role that diet and exercise is going to play in optimizing health and performance in females.”

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