title: Age-related changes in resting energy expenditure in normal weight, overweight and obese men and women.
abstract: OBJECTIVE
  Aging is associated with changes in resting energy expenditure (REE) and body composition. We investigated the association between age and changes in REE in men and women stratified by body mass index (BMI) categories (normal weight, overweight and obesity). We also examined whether the age-related decline in REE was explained by concomitant changes in body composition and lifestyle factors.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  3442 adult participants (age range: 18-81 y; men/women: 977/2465) were included. The BMI range was 18.5-60.2 kg/m(2). REE was measured by indirect calorimetry in fasting conditions and body composition by bioelectrical impedance. Regression models were used to evaluate age-related changes in REE in subjects stratified by sex and BMI. Models were adjusted for body composition (fat mass, fat free mass), smoking, disease count and physical activity.
  
  
  RESULTS
  In unadjusted models, the rate of decline in REE was highest in obese men (slope=-8.7±0.8 kcal/day/year) whereas the lowest rate of decline was observed in normal weight women (-2.9±0.3 kcal/day/year). Gender differences were observed for the age of onset of REE adaptive changes (i.e., not accounted by age related changes in body composition and lifestyle factors). In women, adaptive changes appeared to occur in middle-age (∼47 y) across all BMI groups whereas changes seemed to be delayed in obese men (∼54 y) compared to overweight (∼43 y) and normal weight (∼39 y) men.
  
  
  CONCLUSIONS
  Sex and BMI influenced the rate and degree of the age-related decline in REE. Critical age windows have been identified for the onset of putative mechanisms of energy adaptation. These findings require confirmation in prospective studies.
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK. Electronic address: mario.siervo@ncl.ac.uk.
authors.forename: Mario
authors.initials: M
authors.lastname: Siervo
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Clio
authors.initials: C
authors.lastname: Oggioni
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Jose
authors.initials: J
authors.lastname: Lara
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: Carlos
authors.initials: C
authors.lastname: Celis-Morales
authors.affiliation: Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, Campus for Ageing and Vitality, Newcastle on Tyne NE4 5PL, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Mathers
authors.affiliation: International Center for the Assessment of Nutrizional Status, ICANS Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Sandro Botticelli, 21, 20133 Milano, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Battezzati
authors.affiliation: International Center for the Assessment of Nutrizional Status, ICANS Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Sandro Botticelli, 21, 20133 Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Leone
authors.affiliation: Human Nutrition and Eating Disorders Research Centre, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Via Bassi, 21, 27100 Pavia, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Tagliabue
authors.affiliation: International Center for the Assessment of Nutrizional Status, ICANS Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Sandro Botticelli, 21, 20133 Milano, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Spadafranca
authors.affiliation: International Center for the Assessment of Nutrizional Status, ICANS Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Sandro Botticelli, 21, 20133 Milano, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Bertoli
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D056865:Ideal Body Weight / Q000502:physiology; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*; D050177:Overweight / Q000503:physiopathology; D012146:Rest / Q000502:physiology*; D012737:Sex Factors; D055815:Young Adult
keywords: Aging; Body composition; Indirect calorimetry; Resting energy expenditure