One of the top hormonal changes that can cause weight gain in women is menopause. About 35 percent of American women between 40 and 59 are obese [source: CDC]. When women go through menopause, their estrogen levels drop. Animal studies show that estrogen helps control weight — lab animals whose estrogen levels declined tended to eat more and exercise less. Further, some experts believe a lack of estrogen can throw off the body's ability to properly use starches and blood sugar, which can also result in packed-on pounds [source: WebMD].
Another hormonal imbalance linked to increased fat deposits concerns leptin, a hormone that sends signals to your body that you're full. People who consume too much fructose in their diets (both from natural foods, such as fruit, and from processed foods) can end up with too much leptin in their bodies. Too much of anything isn't good; when your body has too much leptin in it, your brain ignores its signals. Thus you don't realize you're full, and you keep eating [source: Gottfried].