One of the things that happens at menopause is that we lose muscle mass. Muscle burns more calories than fat. So, that is why many of us tend to gain weight at menopause. The way to combat that is to exercise and include weight training as part of your regular routine. That way you can build and maintain muscle and start burning more calories. One of the other things that happens in menopause, is that many women become hypothyroid. It is important to be checked out if you have weight gain and have your thyroid function tested.