title: Changes in leptin and peptide YY do not explain the greater-than-predicted decreases in resting energy expenditure after weight loss.
abstract: BACKGROUND
  It is unknown whether leptin and peptide YY (PYY) influence changes in resting energy expenditure (REE), independently of fat mass (FM) and fat-free mass (FFM) in addition to changes in other energy expenditure (EE) components during weight loss.
  
  
  OBJECTIVE
  The objective of the study was to examine the relationships between leptin, PYY, and body composition with different EE components before and after weight loss and whether changes in leptin and PYY were associated with differences in predicted vs measured REE after the intervention.
  
  
  METHODS
  This was a randomized controlled design.
  
  
  METHODS
  The study was conducted in a laboratory.
  
  
  METHODS
  Participants were ninety-three overweight/obese postmenopausal women (aged 58.1 ± 4.8 y; body mass index 32.1 ± 4.3 kg/m(2)).
  
  
  METHODS
  Interventions included a 6-month caloric restriction diet alone or caloric restriction diet+resistance training.
  
  
  METHODS
  Body composition (dual energy x-ray absorptiometry), REE (indirect calorimetry), total EE (TEE; doubly labeled water), and fasting leptin and total PYY before and after weight loss were measured.
  
  
  RESULTS
  Both interventions yielded significant decreases in weight, FFM, REE, and leptin, whereas a significant time × group interaction was noted for FM (greater decrease in FM in the diet+resistance training group) (P < .05 for all outcomes). No significant differences in TEE, physical activity EE, and PYY were noted between baseline and after the intervention. Age, FFM, leptin, and PYY were the best predictors of baseline REE (R(2) = 0.77; P = .0001), whereas age, FFM, and FM were associated with REE after the intervention (R(2) = 0.88; P = .0001). The same predictors, except for leptin, were significantly related to TEE at baseline (R(2) = 0.70; P = .0001) and after the intervention (R(2) = 0.29; P = .0001), whereas only PYY was a significant predictor of physical activity EE at baseline and after the intervention. Changes in FM and leptin accounted for 27% of the variance in ΔREE (P = .0001). Greater predicted vs measured REE was noted after the intervention (P = .02). However, Δ leptin and ΔPYY were not significant predictors of the differences between postintervention measurement and predicted REE.
  
  
  CONCLUSIONS
  Δ Leptin and ΔFM were strong contributors to changes in REE. However, Δ leptin and ΔPYY were not significant predictors of the differences between predicted and measured REE after the intervention.
authors.affiliation: Behavioral and Metabolic Research Unit (J.M., É.D.), School of Human Kinetics, University of Ottawa, Ontario, Canada K1N 6N5; Department of Nutritional Sciences (A.S.), Faculty of Medicine, University of Toronto and The Hospital for Sick Children, Toronto, Ontario, Canada M5S 3G; Département de Nutrition (R.R.-L.), Faculté de Médecine, and Department of Kinesiology (J.-M.L.), Université de Montréal, Montréal, Québec, Canada H3T 1C5; Institut de Recherches Cliniques de Montréal (R.R.-L.), Montréal, Québec, Canada H2W 1R7; Service d'Endocrinologie (R.R.-L.), Centre Hospitalier de l'Université de Montréal, Montréal, Québec, Canada H2W 1T8; Faculty of Physical Education and Sports (M.B.), University of Sherbrooke, Sherbrooke, Québec, Canada J1H SN4; and Research Centre on Aging, Health, and Social Services Centre (M.B.), University Institute of Geriatrics of Sherbrooke, Sherbrooke, Québec, Canada J1H 4C4.
authors.forename: Jessica
authors.initials: J
authors.lastname: McNeil
authors.forename: Alexander
authors.initials: A
authors.lastname: Schwartz
authors.forename: Rémi
authors.initials: R
authors.lastname: Rabasa-Lhoret
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lavoie
authors.forename: Martin
authors.initials: M
authors.lastname: Brochu
authors.forename: Éric
authors.initials: É
authors.lastname: Doucet
mesh_terms: D001481:Basal Metabolism; D031204:Caloric Restriction; D004038:Diet, Reducing; D015536:Down-Regulation; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy / Q000378:metabolism; D050177:Overweight / Q000178:diet therapy / Q000378:metabolism; D019894:Peptide YY / Q000097:blood*; D012146:Rest; D015431:Weight Loss / Q000502:physiology*
chemical_list: D020738:Leptin; D019894:Peptide YY