Fat cells absorb and release the female hormone estrogen. In women who are overweight, estrogen is not only produced by the ovaries, but also from the extra fat cells in other parts of the body. This release of extra estrogen from extra fat cells upsets the fine balance of the feedback system between the pituitary hormones and estrogen. If the problem can be detected on the bathroom scales, reduce weight to within the normal range for age.
Overweight in men. Heat damages sperm production. In men who are overweight, an excess of flesh at the buttocks, inner thighs, and lower abdomen not only keeps the groin hot, it raises the temperature in the testicles. This reduces their ability to produce vigorous sperm. The testicles should be a few degrees below body heat; hence their cooler position outside the body. Wear loose cotton shorts, and reduce weight to within the normal range for age.
Underweight in women. Being underweight can also upset the feedback system between the hormones. A certain level of fat cells is necessary for hormone production. If bodyweight drops too low, ovulation can be suppressed. Some women athletes and long-distance runners have scanty or absent periods. Avoid crash diets. Avoid any slimming or exercise program which promises a sudden weight loss or one which drops the body weight below the minimum normal range. Increase carbohydrate consumption. Aim for an even body weight within the normal range for age.