Women gain weight or more specifically, body fat, for the same reasons that men do: a surplus of ingested calories in proportion to the amount of physical activity. In more simple terms, you get fatter when you consume more calories than you burn in physical activity. But there is far more to women's weight gain than just an excess of calories. Certain lifestyle practices and habits that are common with women, but not common with men, often tend to produce unwanted weight gain in women. Then there are the hormonal factors. The predominant "sex" hormone in women is estrogen. I say "predominant" because estrogen is produced in both men and women. Bodybuilders and athletes are aware of this, especially when they use drugs, such as certain anabolic steroids and testosterone, that can be converted into estrogen through the actions of the ubiquitous enzyme aromatase. But just as men produce at least 10-times more testosterone than do women, women produce far more estrogen than men under normal conditions. I say "normal" because some bodybuilders who've used large doses of steroids that aromatize have shown estrogen levels that are higher than the typical female. When that happens, certain effects occur in men, such as an increase in the glandular tissue in their breasts or pecs known as gynecomastia. In effect, a man who is producing excess estrogen is growing breasts.
But from a body fat perspective, a lot of myths are still often voiced about the effects of estrogen on body fat gains. It's true that estrogen is responsible for the higher body fat levels in most women compared to men. Estrogen tends to promote subcutaneous fat, or the fat just under the skin. This explains why women usually have softer skin than men. For bodybuilders, the development of subcutaneous fat is considered highly undesirable because that fat will obscure muscular definition. This is the reason why many bodybuilders and athletes on high-dose steroid regimes use drugs to lower estrogen levels, such as aromatase inhibitors. These drugs, such as anastrozole (Arimidex) are most often prescribed to treat estrogen-sensitive breast cancer in older women. But while most men associate estrogen with fat gains, the truth is that estrogen determines how much fat is present in the gut section of men. That is, having deficient levels of estrogen in a man can promote fat in the gut areas.
In women, the higher estrogen levels offer some exercise advantages. For one, having higher estrogen levels promotes a greater release of growth hormone (GH) during exercise. This increase in GH promotes the release of fat from fat cells. Indeed, the greater release of fat during exercise in women explains why they often excel in endurance events, where the ability to tap into more stored fat can favorably . . .