title: Imposed rate and extent of weight loss in obese men and adaptive changes in resting and total energy expenditure.
abstract: OBJECTIVE
  Weight loss (WL) is associated with a decrease in total and resting energy expenditure (EE). We aimed to investigate whether (1) diets with different rate and extent of WL determined different changes in total and resting EE and if (2) they influenced the level of adaptive thermogenesis, defined as the decline in total or resting EE not accounted by changes in body composition.
  
  
  METHODS
  Three groups of six, obese men participated in a total fast for 6 days to achieve a 5% WL and a very low calorie (VLCD, 2.5 MJ/day) for 3 weeks or a low calorie (LCD, 5.2 MJ/day) diet for 6 weeks to achieve a 10% WL. A four-component model was used to measure body composition. Indirect calorimetry was used to measure resting EE. Total EE was measured by doubly labelled water (VLCD, LCD) and 24-hour whole-body calorimetry (fasting).
  
  
  RESULTS
  VLCD and LCD showed a similar degree of metabolic adaptation for total EE (VLCD = -6.2%; LCD = -6.8%). Metabolic adaptation for resting EE was greater in the LCD (-0.4 MJ/day, -5.3%) compared to the VLCD (-0.1 MJ/day, -1.4%) group. Resting EE did not decrease after short-term fasting and no evidence of adaptive thermogenesis (+0.4 MJ/day) was found after 5% WL. The rate of WL was inversely associated with changes in resting EE (n = 30, r = 0.-42, p=0.01).
  
  
  CONCLUSIONS
  The rate of WL did not appear to influence the decline in total EE in obese men after 10% WL. Approximately 6% of this decline in total EE was explained by mechanisms of adaptive thermogenesis.
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: Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Faber
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: School of Agriculture, Food, Science and Veterinary Medicine, Agriculture and Food Science Centre, Belfield, Dublin 4, Ireland.
authors.forename: Eileen R
authors.initials: ER
authors.lastname: Gibney
authors.affiliation: Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK.
authors.forename: Eric
authors.initials: E
authors.lastname: Milne
authors.affiliation: UTNC, Hôpital Larrey, 1, Avenue du Pr. Jean Poulhès TSA 50032, 31059 Toulouse Cedex 9, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ritz
authors.affiliation: Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK.
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Lobley
authors.affiliation: Institute of Human Nutrition, Southampton General Hospital, Mailpoint 113, West Wing, Tremona Road, Southampton, SO16 6YD, UK.
authors.forename: Marinos
authors.initials: M
authors.lastname: Elia
authors.affiliation: Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK.
authors.forename: R James
authors.initials: RJ
authors.lastname: Stubbs
authors.affiliation: Rowett Institute of Nutrition and Health, University of Aberdeen, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Johnstone
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001823:Body Composition; D004734:Energy Metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D022722:Thermogenesis; D015431:Weight Loss / Q000502:physiology*
keywords: Energy expenditure; Metabolic adaptation; Obesity; Weight loss