Does muscle turn into fat?

Philip J. Goscienski, M.D.

January 2010

If muscle turned into fat it would be a strange kind of chemistry, indeed! It does appear that way when we see 50-ish athletes who appear to have transformed their muscles into flab.

A well-toned muscle consists primarily of protein and that includes the dense network of blood vessels that nourish it. It has a deep red color (think filet mignon) and a firm consistency. Fat, on the other hand, is jiggly, yellow, slippery stuff that takes up a lot more space per pound than muscle does.

As an example, a 50-year-old linebacker-turned-couch-potato might weigh about the same as he did when he slammed into an opponent 25 years earlier but he'd never fit into that sleek uniform.

The body doesn't waste energy on muscle tissue that has nothing to do. Dormant muscle fibers and the blood vessels that nourish them simply shrivel. Fat appears when calorie intake is greater than the calories that get burned up in daily activity, insinuating itself between muscle bundles. Thus fat replaces muscle but muscle does not "turn into" fat.

Unused muscles don't stress the bones to which they are attached so the bones become less dense, a condition that may progress to osteoporosis. When muscle fibers waste away they lose the tiny specialized nerve endings that help us to maintain balance. Loss of muscle, loss of bone and loss of balance become the perfect setup for a fracture with even a minor bump or fall. Lack of calcium gets the blame but lack of exercise is the real villain.

That chubby former linebacker probably has a big belly too. That's the worst place to accumulate fat because it means that there is a lot more of the greasy yellow stuff behind those once well-defined abdominal muscles — what young athletes proudly display as a six-pack. No amount of sit-ups will make that six-pack reappear and abdominal fat is associated with heart disease. It's also the source of chemicals that increase inflammation, a major factor in heart attacks.

The good news is that a sensible exercise program can revive long-dormant muscles. They won't regain their youthful size and strength because the hormones that are necessary to build big muscles diminish as we age but it's possible to triple or quadruple one's strength at any age.

Change your thinking. Get rid of the fat and replace it with muscle. You might even see that six-pack again.

Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at