The Consistency in Macronutrient Oxidation and The Role for Epinephrine in the Response to Fasting and Overfeeding.

Context:In humans, dietary versus intra-individual determinants of macronutrient oxidation preference and the role of the sympathetic nervous system (SNS) during short-term overfeeding and fasting are unclear.Objective:To understand the influence of diet and the SNS during 24-h of overfeeding on metabolic changes.Design, Setting, Participants and Interventions:While residing on a clinical research unit, 64 participants with normal glucose regulation were assessed during energy balance, fasting, and four 24-h overfeeding diets, given in random order. The overfeeding diets contained 200% of energy requirements and varied macronutrient proportions: 1) standard (50% carbohydrate, 20% protein, and 30% fat), 2) 75% carbohydrate, 3) 60% fat, and 4) 3% protein.Main outcome measures:24-hour energy expenditure (EE) and macronutrient oxidation rates were measured in an indirect calorimeter during the dietary interventions, with concomitant measurement of urinary catecholamines and free cortisol.Results:EE decreased ...