My husband and I started our new year campaign in earnest. He has done well - a stone and a half lost and four inches off his middle. I've lost a meagre four pounds and my skirts are only a touch more loose. Am I doing something wrong, or is it really easier for men?

Sadly, there is a distinct difference between how men and women store fat and lose weight - it is easier for men. Body shape differences relate to the varying concentration of two hormones, lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL). LPL encourages fat storage while HSL tends to stimulate fat removal, and where these accumulate affects body shape. Men have more fat-storing LPL in their bellies, women tend to have more in their hips and thighs.

When it comes to losing weight, it's down to the hormone receptors - alpha receptors and beta receptors found on the fat cell walls. Alpha receptors inhibit fat breakdown, while beta receptors encourage it. Men tend to have more beta-receptors and fewer alpha-receptors in their midriffs. So, while your husband may have started with a bigger belly, the greater presence of beta receptors will make it easier for him to lose weight and drop inches off his middle. More infuriating is the fact that, even at rest, a man will be burning more calories than a woman, due to his greater muscle mass, which uses more calories than fat cells. My male clients do achieve a faster rate of weight loss, but remember the story of the tortoise and the hare - slowly, slowly can be the best policy. By sustaining your efforts, you may be fitter, trimmer and healthier in the long run.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to Weekend, 119 Farringdon Road, London EC1R 3ER (weekend@theguardian.com).