Cortisol is a steroid hormone produced in the adrenal glands in response to stress. The purpose of cortisol is to provide immediate blood glucose to fuel a “fight or flight” encounter. Under short-term stressful events including exercise, cortisol is a friendly hormone that aids your body’s adaption. The negative results from elevated cortisol levels occur under chronically stressful conditions. Because cortisol suppresses the body’s response to insulin in order to increase blood glucose, long-term elevation can lead to various chronic health conditions including weight gain, obesity, and increased risk for Type II Diabetes. Additionally, cortisol increases production and maturity of visceral fat cells which also contain cortisol receptors, compounding its effects. And, because muscle cells receive less glucose when blood levels remain high, appetite and food cravings increase with elevation of cortisol.
Cortisol has many other physiological effects on the body. With elevated levels, digestion is impaired, absorption of nutrients is diminished, and inflammatory bowel conditions are increased. A common name for stress-related IBS is a “nervous stomach.” Due to vascular changes, specifically constriction of blood vessels, chronic suppression of cortisol can also lead to high blood pressure, atherosclerosis, and fertility disruption in males and females. Another culprit to high cortisol levels is inflammation. Therefore, poor diet and lifestyle habits, such as smoking, that increase inflammation can lead to elevated cortisol and a weakened immune system.
Lifestyle strategies to modulate cortisol levels include anti-inflammatory diets, healthy sleep cycles, stress management, moderate exercise, and rhythmic meal timing. The most widely accepted anti-inflammatory diet is the Mediterranean Lifestyle Plan which includes stress-reducing modes of eating such as dining while seated. This plan also reduces trans and saturated fats, refined sugars, and caffeine. Additionally, it promotes healthy fats from fish, avocados, and nuts as well as high fiber intake from fruits, vegetables, and whole grains.
Another dietary modality to lowering cortisol and increasing the body’s ability to utilize stored fat for fuel is intermittent fasting, or implementing a strict rhythm to the timing of meals. Emerging findings from studies of animal models and human subjects suggest that intermittent energy restriction periods of as little as 16 h can improve health indicators and counteract disease processes. The mechanisms involve a metabolic shift to fat metabolism and ketone production, and stimulation of adaptive cellular stress responses that decrease damage from inflammation, a cortisol-raising stress response.
Our human ancestors practiced circadian rhythms naturally as they were limited to natural periods of daylight and darkness. In addition, food supply was not continual. They naturally practiced shortened periods of eating, long periods of fasting, and much more physical labor during the eating phase. Industrialization has brought devastating consequences to our health and epidemic rates of obesity. The advancements of artificial light, modern agriculture, and technology have resulted in disturbed sleep patterns, over-feeding, nutritionally void processed foods, and sedentary lifestyles. Combined, these upregulate stress, inflammation, and weight gain.
Interestingly, circadian rhythms are cellularly mediated. This hints to our body’s need for patterns to include regular periods of activity with eating, and rest with fasting. When this pattern is disturbed by humans sleeping within fewer and eating within longer hours, cellular changes and gene expressions occur which increase the risk of chronic disease. Studies reveal that disruption of the sleep/wake and fasting/feeding cycle while maintaining an isocaloric diet, still reduced glucose tolerance, increased blood pressure, and decreased the satiety hormone leptin.
Major benefits of intermittent fasting include a better adaptive stress response, improved endocrine function with insulin sensitivity, reduction of age-related neurodegenerative disease processes such as Alzheimer’s, reduced risk of cancer, and reduced inflammatory conditions such as cardiovascular disease, arthritis, and asthma. The reduction in inflammatory markers and free-radical production is attributed both to better mitochondrial function and weight loss. Intermittent fasting may also lessen symptoms related to auto-immune disorders.
Healthy recommendations for intermittent dietary practices include not over-restricting without medical supervision. A modified approach suggests 8-12-hour windows for healthy intake and 12-16 hours for fasting. In addition, the diet should be comprised mostly from the anti-inflammatory guidelines in the Mediterranean Lifestyle Plan. Proper nutritional supplementation can be considered to meet the recommended vitamin and mineral values. And, healthy practices such as ample water intake, daily exercise, and 7-8 hours of quality sleep are necessary for optimal outcomes.