title: Higher 24-h respiratory quotient and higher spontaneous physical activity in nighttime eaters.
abstract: We have previously shown that a higher 24-h respiratory quotient (24-h RQ) predicts greater ad-libitum food intake and that nighttime eaters (NE) ingested more calories during an in-patient food intake study and gained more weight over time. We investigated whether 24-h RQ was higher in individuals who exhibited nighttime eating behavior. Healthy nondiabetic Pima Indians (PI; n = 97, 54 male/43 female) and whites (W; n = 32, 22 male/10 female) were admitted to our Clinical Research Unit. After 3 days of a weight maintaining diet, 24-h energy expenditure (24-h EE), 24-h RQ, rates of carbohydrate (CHOX) and lipid oxidation (LIPOX), and spontaneous physical activity (SPA) were measured in a metabolic chamber whereas volunteers were in energy balance and unable to consume excess calories. Individuals subsequently ate ad libitum from a computerized vending machine for 3 days with amount and timing of food intake recorded. Fifty-five individuals (36%; 39 PI, 16 W) were NE, who ate between 11 PM and 5 AM on at least one of the 3 days on the vending machines. There were no differences in BMI or percentage body fat between NE and non-NE. After adjusting for age, sex, race, fat-free mass, fat mass, and energy balance, NE had a higher 24-h RQ (P = 0.01), higher CHOX (P = 0.009), and lower LIPOX (P = 0.03) and higher 24-h SPA (P = 0.04) compared to non-NE. There were no differences in adjusted 24-h EE or sleep RQ between the groups. Individuals with nighttime eating behavior have higher 24-h RQ, higher CHOX and lower LIPOX, a phenotype associated with increased food intake and weight gain.
authors.affiliation: Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona, USA. gmarci@niddk.nih.gov
authors.forename: Marci E
authors.initials: ME
authors.lastname: Gluck
authors.forename: Colleen A
authors.initials: CA
authors.lastname: Venti
authors.forename: Arline D
authors.initials: AD
authors.lastname: Salbe
authors.forename: Susanne B
authors.initials: SB
authors.lastname: Votruba
authors.forename: Jonathan
authors.initials: J
authors.lastname: Krakoff
mesh_terms: D000328:Adult; D050260:Carbohydrate Metabolism / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007198:Indians, North American; D050356:Lipid Metabolism / Q000502:physiology; D008297:Male; D010101:Oxygen Consumption; D015430:Weight Gain