Most weight loss research is centered on exercising more and eating less. However, there may be another cause of weight gain. Hormones--chemicals released by one or more cells in response to a condition in the body, which act on another organ or organs to change that condition--may contribute to weight gain. If you have been exercising and dieting and have not seen positive physical changes, look to your hormones for an explanation.
Hormones control the functioning of your organs, including growth, development and reproduction. Fat gain is regulated by your hormones because hormones influence the way your body uses and stores calories, as well as control the volume of salt and sugar in your bloodstream. All hormones circulate throughout your body, and each hormone influences specific organs and tissues. Additionally, all hormones are present in both men and women, but the levels, function and placement of these hormones vary by gender. Increased or decreased levels of any hormone can cause major changes, such as fat gain.
Estrogen is known as the female sex hormone. A decreased estrogen level is often the reason for weight gain in menopausal women. During menopause, estrogen declines rapidly, causing your body to stop ovulating and slowing your metabolism. In men, high levels of estrogen cause low levels of testosterone--the hormone that helps create lean muscle mass. Fat cells in your body can produce estrogen, so your body works harder to convert calories into fat to increase estrogen levels. Unfortunately, fat cells do not burn calories the way muscle cells do, which causes you to gain weight.
Research done by the Mayo Clinic states that testosterone levels decrease as you age--about 1 percent a year after age 30 on average. Testosterone helps your body to create lean muscle mass out of the calories that you take in. Muscle cells burn more calories than fat cells do, increasing your metabolism and helping you maintain a healthy weight. When levels of testosterone drop, your body loses muscle tone and your metabolism slows.
Progesterone is most often associated with women because it helps to induce bleeding during menstruation. Levels of this hormone reduce with age, particularly in menopausal women. One characteristic of menopause is a slowed metabolism; lower levels of progesterone--which functions like testosterone--can cause weight gain. In men, progesterone is converted to testosterone. Since progesterone levels decrease with age, testosterone levels also decrease, contributing to weight gain.
Androgen hormones (including testosterone) cause the normal changes of puberty in boys' bodies and then influence sperm-cell formation, sexual interest and male pattern baldness. Females produce trace amounts of androgen in the adrenal glands as well as in the ovaries. Increased levels of androgen--due to overproduction by the adrenal glands in women, and increased age in men--cause you to gain weight around your abdomen instead of around your lower half. This weight gain is often referred to as “middle-age spread.”
Insulin is a regulatory hormone that is released in the pancreas and regulates glucose, fat and protein metabolism. If your body is insulin resistant, it will mistakenly turn every calorie you consume into fat, thus causing weight gain.