If Leptin regulates overall body mass, what factors are responsible for women’s and men’s different body shapes? Classically, women look like pears and men like apples. Women carry more fat ”on” their bodies and deposit most of it in three areas: breasts, hips, and buttocks. Men, on the other hand, carry their fat “within” the body; they tend to accumulate it in the abdominal area and around the intestines. Androgens (the male hormones, one of which is testosterone) also make men’s muscle mass higher and their bodies heavier than women’s.
This sex-specific distribution of body fat is determined importantly by our hormones: the more androgynous a person is, the more he or she is inclined to deposit fat around the midsection. Women with polycystic ovary syndrome (an endocrine problem characterized by infertility, obesity and a male distribution of body hair) have higher levels of androgens than average women and significantly higher waist-hip ratios (the circumference of the hips). Some aspect of hormone balance is genetic. Of all women measured in the European Fat Distribution Study, Mediterranean women had the highest free testosterone concentrations and the greatest abdominal girth.
As any woman who has borne a child can tell you, body shape changes significantly with reproduction. The cause changes in the activity of an enzyme involved in the metabolism of fat (lipoprotein lipase) and in the sensitivity of fat cells to insulin. Body fat is redistributed during pregnancy, when the amount of fat in the upper legs decreases in the third. If the new baby is nursed, the mother accumulates fat in the breasts, upper arms, and upper trunk. By about six months after lactation her body fat distribution returns to baseline levels.
Legato, M.J. (2002) Eve’s Rib The Groundbreaking guide to Women’s Health, Open Road Integrated Media, Inc. Ch. 4 pg. 78