Does cortisol increase muscle loss?

It's a popular idea that high levels of cortisol promotes muscle loss. However, there is evidence to show that despite elevated levels of cortisol, muscle loss is not inevitable.

Cortisol levels following several months of aerobic exercise, for example, are far higher than when aerobic exercise and weight training are combined.

Some evidence for this comes from a trial published in the Journal of Applied Physiology [1]. A group of 31 women was assigned to one of four groups.

• The first group served as a control group, and did nothing.

• Group two followed a low-fat, high-carbohydrate diet.

• Group three combined the diet with aerobic exercise.

• The fourth group combined diet with aerobic exercise and a regular strength training program.

When cortisol levels were measured at the end of the study, they had risen by an average of 51% in group three (the group combining diet and aerobic exercise). The women who combined aerobic exercise with a strength training program only experienced a 10% rise.

However, the loss of body fat was greatest in the women who combined a low-calorie diet with aerobic exercise. They also gained more muscle (3.1 pounds) than the women who trained with weights, who actually lost 3.7 pounds of muscle.

In a similar study, moderately obese subjects were assigned to one of three groups: diet plus strength training, diet plus aerobic training, or diet only. Subjects in the two exercise groups trained three times per week [2].

After eight weeks, the average amount of weight lost, 19.8 pounds, did not differ significantly among groups. The strength-training group, however, lost significantly less muscle than the aerobic and diet-only groups.

Related Articles

• Belly Fat and How to Beat It
• How to Fight Fat and Win (Members Only)
• The Maximum Muscle Plan (Members Only)
• The Myth about Muscle and Your Metabolic Rate

Reference
1. Kraemer, W.J., Volek, J.S., Clark, K.L., Gordon, S.E., Incledon, T., Puhl, S.M., Triplett-McBride, N.T., McBride, J.M., Putukian, M., & Sebastianelli, W.J. (1997). Physiological adaptations to a weight-loss dietary regimen and exercise programs in women. Journal of Applied Physiology, 83, 270-279
2. Geliebter, A., Maher, M.M., Gerace, L., Gutin, B., Heymsfield, S.B., & Hashim, S.A. (1997). Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects. American Journal of Clinical Nutrition, 66, 557-563