Muscle Atrophy: What You Should Know About Muscle Mass Loss And Eating Disorders

Eating disorders take a huge toll on the human body. In many ways, the most severe effect of any eating disorder is the loss of muscle mass that is caused by anorexia nervosa (and to a lesser extent, bulimia nervosa). Here are four things everyone who has anorexia or who cares for someone who has anorexia needs to know about the effects of this eating disorder on the muscles.

The most deadly complication of anorexia is loss of muscle mass

More specifically, the most deadly complication of anorexia is the loss of heart muscle mass. As the body is deprived of protein and carbohydrate, it loses muscle mass. It loses muscle mass faster in the heart than in other skeletal muscles. As the heart gets smaller and weaker, it loses its ability to pump harder in response to stress. Exercise no longer raises the heart's rate as high as it did before the onset of anorexia. Eventually, the heart loses is ability to respond to stress altogether. The pulse accelerates as the heart makes little pushes of blood through the circulatory system, but blood pressure falls. The combination of fast pulse and low blood pressure indicates an advanced stage of disease.

Loss of muscle mass is caused by carbohydrate deficits, not just protein deficits

Most of us think in terms of protein when we think of muscle-building food. But carbohydrate is just as important to maintaining the size and shape of healthy muscles. Each muscle cell maintains its own supply of stored energy in the form of glycogen. Glycogen is a chemical combination of glucose and water, one molecule of glucose combined to four molecules of water. The muscle cell can break down glycogen when it needs energy faster than the bloodstream can deliver it.

When the muscle cell is not using glycogen for energy, it serves to "pump up" the cell, giving muscles bulk. Amino acids from protein go into creating the fibers that give muscles their strength while glucose from digested carbohydrates combines with water to give muscles their bulk. Deficits of protein or carbohydrate as well as dehydration all contribute to muscle wasting.

Bulimics lose muscle mass even when they get enough calories

Muscles need periodically to be "closed for maintenance". Aging cells are exposed to free radicals that damage proteins. Sometimes they acquire mutations in their DNA or RNA that cause the formation of dysfunctional proteins and enzymes. When a muscle cell has a period of 12 to 18 hours or more in which it does not have to process incoming nutrients, it can go through a process called autophagy, or "self eating". The cell recycles defective proteins and makes new proteins in their place. People who binge and purge never give their bodies a break from food. Their cells do not have a chance to go through autophagy. As a result, they have smaller and weaker muscles than their nutrient consumption would support.

Muscle atrophy sets off a cascade of orthopedic problems

In the spine, the result can be slipped disc. Without the right tension on the spine, the vertebrae get out of line. The "shock absorbers" between the vertebrae, the discs, can be put under unusual pressure. This may break the their protective coating so the disc goes flat, something like a flat tire. This may cause the vertebrae to press against a nerve and cause severe pain. 

For instance, if the muscles in the neck atrophy, the fail to maintain the right amount of pressure on the cervical spine. If these discs get out of alignment, the bony protuberances at the side of a vertebra may put pressure on a brachial nerve. This nerve carries electrical signals from the central nervous system to the shoulder, arm, wrist, and hand. Even if the muscles in the shoulder, arm, wrist, and hand are still relatively healthy, there can be constant pain from the pressure on the nerve because the neck muscles atrophied.