Cortisol: The Two-Faced Hormone

What is cortisol?

Cortisol is a hormone that belongs to a family of steroid hormones known as glucocorticoids. It’s secreted by the adrenal cortex, which is located in your adrenal glands that sit atop your kidneys. Cortisol is the main glucocorticoid in humans.

Glucocorticoids affect every cell in the body so needless to say, they’re pretty important.

In particular, glucocorticoids released in the body send feedback to the brain and influence the release of CRH (corticotropin-releasing hormone) and ACTH (adrenocorticotropic hormone). ACTH stimulates the adrenal glands to secrete cortisol. The rise in cortisol secretion follows ACTH release after a 15-minute to 30-minute delay.

Cortisol plays some very positive and vital roles including energy regulation however as fat as muscle development goes it carries some very negative effects such as muscle protein breakdown when its levels are high for a prolonged time.

Cortisol accelerates the breakdown of proteins into amino acids (except in liver cells). These amino acids move out of the tissues into the blood and to liver cells, where they are changed to glucose in a process called gluconeogenesis. Therefore a prolonged high blood concentration of cortisol in the blood results in a net loss of tissue proteins and higher levels of blood glucose.

Cortisol and Exercise

Cortisol is known as a “stress hormone” because of it’s secretion response and function when the body is stressed. Because exercise is a physical stressor on the body, it triggers a cortisol response.

Acute high intensity resistance exercise is associated with increased plasma cortisol concentration. In other words, after something like a sprint or a high-intensity conditioning or bodybuilding-style workout, plasma cortisol concentration increases. The response is similar to that seen of growth hormone. The most dramatic increases occur when rest periods are short and total volume is high.

Aerobic endurance training, particularly running, is linked with protein loss from muscle (partially induced by cortisol). Endurance trained individuals typically have a higher cortisol response, while resistance trained individuals have a higher testosterone response.

Daily Cortisol Pulses and Meal Timing

The degree of cortisol release during high intensity exercise depends in part on the time of day and the timing of meals. When exercise is performed during a time of already high cortisol levels (for example, in the morning), it doesn’t increase above already elevated levels.

Cortisol secretion displays 7 to 15 spontaneous or meal-associated “pulses” throughout the day. Cortisol secretion rhythms are closely coupled to the sleep-wake cycle. Peak cortisol release occurs between 7 and 9 in the morning, the time of dark-light transition.

The chart above shows typical cortisol levels over a 24hour period

Cortisol & Insulin

Understanding the interactions between these two hormones is important. Technically speaking, cortisol is both a fat storing and fat burning hormone. This is because it increases the activity of lipoprotein lipase (LPL), the body's major fat storing enzyme. But it also increases the activity of hormone sensitive lipase (HSL), the body's chief fat releasing enzyme.

Growth hormone and catecholamines, which are higher during exercise and fasting periods, accentuate cortisol's fat burning potential while suppressing its fat storing potential. In the fed state, when insulin is around in high amounts, HSL activity is turned way down while LPL activity is cranked up. In this way, insulin magnifies cortisol's fat storing properties while blocking its fat burning activity.

Stress and Cortisol

Stress (both psychological and physical) can result in the “alarm reaction.” If stress is ongoing, this can cause enlarged adrenal glands and atrophied lymphatic organs. When adrenals enlarge, they can produce excessive cortisol; when lymphatic organs shrink, they create fewer white blood cells. The immunosuppressive effects of intense exercise have been attributed to high plasma cortisol concentrations that prevail after prolonged intense exercise.

Acute Versus Chronic Cortisol Release

It’s important to distinguish between acute and chronic cortisol release. When muscle glycogen concentrations are low, cortisol is released and fuel use shifts toward protein or fat so that judicious use is made of the little glucose that remains.

In the long-term, excessive cortisol will encourage fat synthesis and storage, along with provoking appetite.

The acute increases in cortisol following exercise also stimulate acute inflammatory response mechanisms involved with tissue remodelling. In the short term, this is a necessary response that helps with repairing damage produced by training. Only long-term cortisol elevations seem to be responsible for adverse catabolic effects.

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// Are you struggling to lose body fat (particularly around your stomach? Are you constantly tired? Are your struggling to improve your muscle tone, strength and muscle gain or worse still are you losing quality your hard earned muscle? If the answer to any of these questions is yes THEN UNMANAGED CORTISOL LEVELS COULD BE THE CAUSE.

Download my hormone guide and find how to optimise your cortisol levels so you can accelerate fat loss, improve your muscle and boost your energy levels.