Skin collagen and collagen density were measured in addition to dermal thickness (11). The skin of men demonstrated a gradual thinning with advancing age (12–93 years), whereas the thickness of women’s skin remained constant up until the .fth decade, after which it decreased with age. The male forearm skin contained more collagen at all ages in the range 15–93 years.

In both sexes there was a linear decrease in skin collagen with age. Collagen density calculated as the ratio of skin collagen to thickness was lower in women at all ages. The rate of collagen loss was similar in both sexes. Women start with lower collagen content; therefore they seem to age earlier than men. Collagen density, representing the packing of brils in the dermis, is lower in women than in men. This may be due to androgen, since skin collagen density is increased in patients with virilism.

Forearm skinfold thickness, as measured by a caliper, decreases starting at age 35 for women and 45 for men. Starting at age 35, it is thinner in women than in men (12). In younger subjects 17–24 years, forearm, thigh, and calf skinfold thickness in women is lower than in men (13).

Heel pad thickness, an indicator of soft tissue thickness in the body, was thicker in Ethiopian men than in women (14). Skinfold compressibility in Japanese students was greater in women than in men at the pectoral site, and smaller at nuchal, submental, biceps, thigh, suprapatellar, and medial calf sites (7). The changes in the distribution of fat between the ages of 6 to 18 years were studied in 2300 subjects (15). Up to 12 years of age, there was no difference between the two sexes: the mass of the subcutaneous fat increased more than threefold, while that of the internal mass increased less than twice. After the age of 12, the relative mass of the subcutaneous fat continued to increase in girls but not in boys.

The distribution of fat over the body is different in men and women (16). In men, an increase in fat tends to accumulate in the abdominal region and upper parts of the body, whereas in women it is located in the lower body, particularly in the gluteal and femoral regions. In addition, the proportion of body fat is higher in non-obese women than in non-obese men. The characteristic difference in body fat distribution between the sexes exists both in non-obese and obese subjects.

Lipoprotein lipase activity and mRNA levels were higher in women in both the gluteal and abdominal regions. In women, higher enzyme activity was found in the gluteus than in the abdomen, whereas in men it was higher in the abdomen. These regional and sex differences in lipoprotein lipase activity might underlie the difference in fat distribution and total fat content. Variation is at both the mRNA level and posttranslational level.