The short-term effects of fasting on the neuroendocrine system in patients with chronic pain syndromes

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/m(2)) 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/m(2)) received a vegetarian-based diet. With fasting significant increases of the urinary concentration of noradrenaline (17.8 +/- 3.0-27.8 +/- 3.8 mug/ml), adrenaline (1.5 +/- 0.2-3.4 +/- 0.7 mug/ml) and cortisol (26.1 +/- 3.7-40.7 +/- 6.1 mug/ml) were observed, whereas controls showed no significant endocrine changes. The neuroendocrine response to fasting was pronounced in younger subjects (age <50 years) and in the presence of a BMI >25 kg/m(2), 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.