Answer: Gender & hormonal differences play major roles in the different fat storage patterns of men and women. Some researchers believe the historical roles of men and women in hunter/gatherer societies may have influenced this. Men were typically the hunters, having to run after (or from) prey. Moving fat on the arms and legs would have a much higher metabolic cost (meaning it would have taken more energy), which would be problematic when food was scarce. This is the reason, the theory continues, for a more central, abdominal storage area in men. It is easier and less calorically "expensive" to move. Women, of course, store fat in breast and hip areas with the hips and legs accumulating much of the body fat during adult weight gain. From an evolutionary standpoint, breasts were necessary for successful reproduction and hips were designed to help carry offspring during pregnancy.
As we age and hormone levels change, body fat may find new, preferential areas to settle. When weight gain continues, as it often does during a major portion of our adulthoods, fat often begins to accumulate intramuscularly and intra-abdominally (also known as visceral fat). An increase in “belly fat” is a sign of this and is considered a risk factor for heart disease and other metabolic diseases such as insulin resistance, high blood pressure, dyslipidemia and Type II diabetes. Because this fat lies buried within the body, it is not measured with devices such as calipers.