The Short-term Effects of Fasting on the Neuroendocrine System in Patients with Chronic Pain Syndromes

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Abstract
It is commonly reported that short term fasting leads to mood enhancement and emotional harmonisation. We investigated psychosocial well-being and the neuroendocrine response, assessed by nightly urinary excretion of cortisol and catecholamines, in 28 inpatients with chronic pain syndromes during and after a one-week modified fast. Twenty-two of the patients (51.4±2.7 years, BMI 26.8±1.0 kg/m2) participated in a 7-day fast with daily intake of 300 kcal/day, six control patients (47.5±4.0 years; BMI 22.9±1.1 kg/m2) received a vegetarian-based diet. With fasting significant increases of the urinary concentration of noradrenaline (17.8±3.0-27.8±3.8 μg/ml), adrenaline (1.5±0.2-3.4±0.7 μg/ml) and cortisol (26.1±3.7-40.7±6.1 μg/ml) were observed, whereas controls showed no significant endocrine changes. The neuroendocrine response to fasting was pronounced in younger subjects (age 25 kg/m2, moreover the increase in cortisol excretion was significantly higher in subjects with lower baseline cortisol levels. Mood and well-being increased non-significantly in both groups. Fasting was well tolerated, and regarded as beneficial by most fasting patients. Our results show that short-term fasting leads to neuroendocrine activation and may suggest that the extent of this response is dependent on the individual metabolic and endocrine state at baseline.