How good is exercise for weight loss? It might depend if you’re a man or a woman

Everyone knows exercise helps you lose weight… but it’s not as simple as that, according to new research that highlights a huge potential divide in the way men and women respond to a workout.

A group of male and female rats were all fed a high-fat diet, and half of them were trained to run on a treadmill. After 10 weeks, “remarkable” differences emerged between the sexes.

The males who exercised ate less food and gained less weight than those who lazed about doing nothing — as you’d expect, right, since it’s well-established exercise suppresses appetite and assists with fat loss.

Except the female rats who exercised didn’t eat any less, and ended up weighing the same as the sedentary females.

When the study was repeated, but the males were fed a low-fat diet instead of a high-fat diet, the impact of exercise on body weight emerged even faster.

The experiments suggest there are big differences between the sexes when it comes to the effects of exercise, and how it influences the hormonal signals and brain processes that regulate appetite.

Researcher Rebecca Foright, a graduate student from the University of Colorado, said her study highlights a big problem in a lot of scientific research: many experiments rely on data drawn from male mice, and overlook the different results that may come from female mice.

RELATED: Younger generations struggle more with weight loss than their parents

“It is unacceptable to simply assume that females will respond to interventions in the same manner as males,” she said in a statement. "I hope that this research inspires other investigators to examine a female-specific response in their animal models.”

She’ll present her research this week at the Society for the Study of Ingestive Behavior's annual meeting in Montreal.

It’s worth noting this finding isn’t entirely surprising — despite what many people believe, exercise isn’t the most effective path to weight loss (and nor can you justify eating whatever you like just because you work out a lot. Disappointing but true).

That’s because exercise burns way less calories than assumed: your day-to-day physical activity accounts for only around 20 to 30 percent of your body’s total energy use, even if you’re a workout demon.

While exercise is super important for your overall health, when it comes to straight-up fat loss, it’s smarter to focus on your diet — which, as a general rule, means eating less calories than your body burns for energy.

RELATED: Hunger hacks: 15 foods that suppress your appetite naturally