Well, as pointed out above, women have significantly more in percent body fat than men.

I have heard of people talking about folks with 0 percent body fat. Can't be done. Cell membranes are made up of phospholipids or fats. Nervous tissue is largely lipids. Without some fat, your tissues would be like jello and you wouldn't have any brains.

Men are pretty much at their minimum % body fat at 5% which is about what body builders shoot for when they compete. The less fat they have, the better their muscles show up. The muscles are not obscured by a thin layer of fat under the skin. Men are pretty lean at 10% body fat. With men, anything at or under 15% is fine.

Women seem to hit their minimum body fat at 10%. Anything under 15% usually shuts down their reproductive system. Any woman who is under 20% body fat is doing just fine. Women need to have at least a certain amount of calories to go through a pregnancy successfully. So a bit of fat means a greater fertility. Maybe Rudens with his plump nudes was onto something.

There are various ways to estimate body fat but none of them is accurate. The hydrostatic test is generally touted as the gold standard. But I knew a woman who started cycling, lost 10 lbs (she was not at all plump), put on muscle and did a before and after hydrostatic test. She supposedly increased % body fat. I figured that the aerobic fitness had increased her lung capacity which would have been interpreted as increased fat in the test. I think a caliper test works just fine for caparative purposes. Shoot even an informal skin fold pinch between your navel and crown of the pelvis works fine for the "am I losing fat" question. To really get the right number, you have to measure the fat. The best way is to take the person, throw them into a blender and skim off the fat and weigh it. But that is a bit drastic and you don't get too many people who opt to use it.


As people age, they tend to lose about 1% of the aerobic capacty and 1% of their muscle mass per year. People also tend to get a slower metabolic rate as they age. People also tend to gain weight as they age. So they get heavier but have less muscle which means their percent body fat tends to go way up. The good news is that regular aerobic activity and some weight training can almost halt the loss. Also even people who are advanced middle aged (which is a nice way of saying "old") can with exercise regain quite a bit of what they lost.