The Hour Between Dog and Wolf: How Risk Taking Transforms Us, Body and Mind

by John Coates

It is during our downtime, when catabolism is turned off, that anabolic hormones step in and rebuild our depleted energy stores so that we have fuel to draw on next time we are called into action. These anabolic hormones include testosterone and growth hormone, which together convert amino acids into muscle and calcium into bone; insulin, which removes excess glucose from the blood and deposits it in the liver; and a chemical called insulin-like growth factor (IGF), which rejuvenates cells throughout the body and brain. A healthy person, and to a greater extent a tempered athlete, will have a high ratio of anabolic to catabolic hormones, a ratio known as the growth index. A high growth index indicates a robust capacity to rebuild one’s body after a period of destruction, a condition that Bruce McEwen, together with Elissa Epel and Jeannette Ickovics, has termed “thriving.”