How many times have you heard female friends complain that their husbands have an easier time losing weight. All he has to do is hit the gym and his weight just comes off, she kills herself working out and the weight is slow to come off if at all? It’s a complaint I hear all the time in the clinic. I’ve often written it off as formerly more athletic men rediscovering their muscle memory and such.

It turns out there’s something to this. Enough something that Todd Hagobian and Barry Braun gathered all the studies they could find looking at sex differences and exercise into a review article in the current issue of Exercise and Sports Medicine Reviews.

Aggregating the result of several studies, the authors first looked at hormonal and body composition changes with exercise. In both rat and human studies researchers have found that if food is readily available even when exercising the same amount, males will lose body fat and females won’t. It turns out that due to hormonal differences with exercise, the appetite of males can actually be suppressed by exercise while females naturally are wired to preserve body fat and hunger increases. The hormonal changes are more subtle than just appetite as females have a different response in terms of overall energy balance but the net effect is clear.

All this is aggregated data, of course, and the authors note that no single study address hormones, appetite and actual food intake together. Every study has carved off a few pieces of the puzzle. The picture does crystalize though to show that women have a tougher time losing weight with exercise and without dietary discipline.

His Take: I counsel patients every day about this problem. I encourage every patient to learn how to eat. Dietary discipline (controlling the number of calories consumed) is at least as important as exercise. We know that diet alone doesn’t work for long but at least for women exercise alone isn’t enough either.

Her Take: It’s nice to know there is now research that supports what I have suspected for a long time — the female body is designed to hoard calories. Again, maintaining a healthy weight means paying attention to both what you eat and what you do.