Long Steady Distance / Low Calorie Diets, Cortisol and Brain Aging

Last summer Tony agreed with me that I was probably killing myself with all the cycling I was doing. Soon there after I wrote Shortening your life by too much exercise to capture what I call the finite beat hypothesis – the heart has the potential for a certain number of beats and once these beat occur the heart stops working. It is a theory that seemed to make sense to me at the time.

In September when I started working at SST it became evident that the volume of cycling that I was doing was slowing my muscle growth because of the high level of cortisol associated with exercising longer than 45 minutes. Once I dropped down to one cardio session per week my lean body mass started to increase. If cortisol can have that dramatic an impact on lean mass creation what impact does it have on other body tissues?

A devastating impact.

Stress hormone may speed up brain aging outlines the findings of a recent study on an elderly population. The goal of the study was to determine if there was a relationship between cortisol levels and hippocampus size and neural density. The hippocampus is a part of the brain that is implicated in memory and spatial awareness functioning. It has long been known that in most individuals, there is a decrease in hippocampus size as they grow older and, as a consequence, ones performance on memory and spatial awareness tasks decreases with age. However, this new study indicates that the degree of deterioration is related to cortisol levels such that those individuals who have higher levels of cortisol show greater impairment and the size of their hippocampus is reduced when compared to those individuals who have lower cortisol levels.

What are the practical implications of this finding?

If you want to keep your brain functioning at a high level for the duration of your life you need to decrease the amount of stress you experience. This doesn’t just mean psychological or mental stress, it also means physiological stress.

Steady state cardio sessions that last more than 45 minutes have been shown to increase cortisol levels as have intense resistance and strength training sessions of the same length. Limit the length of these to less than 45 minutes and if you can’t, make sure you consume some simple sugars during the sessions to mitigate the bodies natural cortisol release in response to a drop in blood sugar level.

Very low calorie diets or eating behaviours that include not eating for more than 4 hours in a row should be avoided as they will cause a release of cortisol.

You should eat within 20 minutes of waking to help lower the level of cortisol in your body – cortisol is very high in the morning because you have not been eating. The sooner it is reduced, the sooner the negative aspects of cortisol will be eliminated.

Remember that cortisol is a wasting hormone that causes your body to consume itself to maintain functioning. When cortisol levels are high very little of your body will grow and we now know that this includes your brain. If you want to maintain a high quality of life into your senior years you need to avoid activities that promote cortisol release when you are younger.