Just what does “low body fat” mean, if there’s a such thing as “skinny fat,” and is a person with low body fat necessarily what we’d consider as thin or skinny?

A person can have extremely low body fat, but not the appearance of someone who is thin.

However, what goes hand-in-hand with very low body fat is a very trim waistline.

Think Arnold Schwarzenegger during his competitive Mr. Olympia days; he had massive shoulders and arms, huge slabs of muscle in his back, bulging thighs, yet the tiniest waist.

A competitive male bodybuilder, certainly far from having a skinny appearance, will often maintain a year-round body fat percentage of between 8 and 12 percent, which is low for a man.

A 5’7” woman who seriously strength trains and has a “clean” diet may weigh 140 pounds yet have a body fat percentage of just 12 percent … which is borderline “essential,” but at 140 pounds, she’ll hardly look scrawny.

However, she’ll have a very lean, tight waist and easily slip into a size 6 or possibly 4 pair of jeans.

Thin by common standards, but also a hard body. Shutterstock/OSTILL is Franck Camhi

An identical height woman may weigh 115 pounds yet have 20 percent body fat. She will appear thinner than the muscular woman and will more easily fit into a size 4, possibly size 2 pair of jeans.

If both women are wearing leggings, the 115-pound woman will have the thinner legs.

She will have the thinner arms and narrower upper back. However…the muscular woman will probably have a smaller waist circumference, but the muscle in her thighs will prevent fitting into the size 2 jeans.

The lighter woman is “skinny fat.” She looks thin but has 20 percent body fat, and thus, once those leggings come off and her legs are visible, you will see that they have a soft, perhaps a mushy, appearance, maybe even some cellulite.

Thin by common standards, but also lacking tone.

The heavier woman with the very low body fat percentage will have hard, very tight legs, and the individual quadriceps muscles will show.

In fact, the separation of the hamstring muscles in the back of the legs will be visible.

And she’ll have visible veins in her arms, while the “thin” woman may not have any veins showing at all.

This all isn’t to say that a person who is skinny in appearance can’t at the same time have very low body fat.

They most certainly can, as in the case with people who have anorexia nervosa.

When this sickness gets progressed enough, the individual is down to skin, bones and wasted muscle, with marginal body fat still existing … well into the single digits percent-wise.

More than thin; looks like an eating disorder.

Competitive marathon runners and high jumpers also have very low percentages while appearing thin.

A woman who competes in a physique contest will also have body fat in the single digits.

However, she also has considerable muscle, and the single-digit body fat reading promptly goes up once the contest is over because the athlete resumes eating more.

Getting it down that low usually begins several weeks or a few months prior to the contest, and the dieting at this point is carefully planned for maximum nutrients.

Lorra Garrick is a former personal trainer certified through the American Council on Exercise. At Bally Total Fitness she trained women and men of all ages for fat loss, muscle building, fitness and improved health.