Although the construction of male and female fat cells is basically the same, they differ vastly when it comes to size and function. To begin with, women’s fat cells are five times larger than men’s! In addition, not only are women’s cells capable of holding more fat, they are genetically programmed to do so. It all comes down to enzymes:
Even though these enzymes are present in both men and women, women’s bodies have two times the number of lipogenic (fat-storing) enzymes, and only half the number of lipolytic (fat releasing) enzymes. This is the genetic legacy of women’s role as the childbearing gender of the species. Nature wanted to ensure that women carried enough fat cells to nurture their growing babies and to breast-feed them after they were born. A baby inutero requires the mother to burn at least 300 extra calories a day, and breast-feeding can require as much as 500 extra calories.
In addition to supplying the normal caloric needs of a baby, our foremothers also stored extra body fat in case of drought or famine. This extra fat was stored in the hips, thighs, and buttocks. Therefore, the females who survived famine and drought to pass down their genes were the women whose bodies were adept at storing fat. Skinny thighs in the past were a serious liability, serving only to increase the risk of death when food supplies became scarce.
These enzymes tend to be balanced in a healthy person. Too much of either type develops an unbalanced system and leads to insulin resistance, a prime contributor to stubborn fat.