Are you smack-dab in the middle of a perfect Body Mass Index? When most people look at you, do they assume you're the perfect weight and in impeccable health?

Do you have a fixation with your weight and thinness, and have you even convinced yourself that you are the picture of health?

Unfortunately, that may not be the case. If you look slim and deceptively fit in your clothes, but like a Chinese Shar-Pei when naked, then you're skinny fat.

That's right, skinny fat. So what exactly is skinny fat, you ask? Skinny fat is when you look reasonably fit and healthy in your clothes but underneath those cool duds, your muscles are like a jiggly bowl of Jell-O.

While it sounds like an oxymoron, skinny fat is simply carrying more fat and insignificant amounts of muscle on an otherwise thin body. Men and women who lose weight exclusively from dieting, and especially those who avoid weightlifting, are prone to being skinny fat.

Paradoxically, many people, even after weight loss, are extraordinarily unhappy with their bodies. Why?  Because they focused exclusively on weight and clothing size and were likely unaware of the significance of body composition.

What is body composition?  Body composition is your body's lean-to-fat ratio, or how much muscle vs. fat you're carrying.  For example, typical athletes carry optimal levels of body fat that range from 14 percent to 24 percent for women and from 6 percent to 15 percent for men.

They say the devil is in the details, and therein lies the problem with the BMI. The index is quick and dirty and based primarily on your height and weight. Body fat percentage would be far more accurate.

What's the solution to skinny fat? You guessed it — exercise! And, no, I don't mean endless hours of cardiovascular exercise. If you want to be lean and toned, you have to invest in serious strength training, otherwise known as weight training, bodybuilding, or weight-bearing exercise. Strength training will make you stronger, increase your muscle mass, and improve your muscle tone. There are no ifs, ands, or buts about it: Strength training is the key to ridding yourself of skinny-fat syndrome.

And another thing:  If you're skinny fat, don't worry about losing fat, just focus primarily on gaining some hard-earned body-shaping muscle.

If you want to get technical about it, you can get a body composition analysis test using skin-fold calipers at your local gym.  If you want to take it up yet another notch, head to Temple University for a hydrostatic body composition analysis, which is a fancy way of saying underwater weighing.  Experts say it's the gold standard for measuring body composition.

If you're skinny but you have more gut than butt, can pinch an inch, or you're sporting a muffin top, it's time to get serious about gaining some muscle mass. A cross-training fitness regimen — high-intensity cardiovascular exercises like jumping rope followed by serious strength training three times a week — should yield some tangible results.

And if you're skinny fat, why should you care? You may be skinny, but that alone will not save you from high cholesterol, heart disease, and other conditions associated with inactivity.

Just because you're skinny doesn't mean you're healthy.