Why exactly do humans lose subcutaneous fat tissue with age? It appears that we either lose fat cell volume or we might actually be losing the number of fat cells with age.
One hypothesis is that as the vascular system weakens with age, the fat cells on the perimeter of the body shrink and die because they don't have enough blood flow to sustain them. The problem with this hypothesis is that subcutaneous fat loss is very gradual and starts during young adulthood and continues. It also happens in very fit individuals too.
Another hypothesis I read before was that subcutaneous fat is loss because of a drop in estrogen levels after menopause. This hypothesis doesn't explain why men lose subcutaneous fat with age. Also, women start to lose fat on their hands and upper cheeks long before menopause starts.