title: Body composition and energy expenditure predict ad-libitum food and macronutrient intake in humans.
abstract: BACKGROUND
  Obesity is the result of chronic positive energy balance. The mechanisms underlying the regulation of energy homeostasis and food intake are not understood. Despite large increases in fat mass (FM), recent evidence indicates that fat-free mass (FFM) rather than FM is positively associated with intake in humans.
  
  
  METHODS
  In 184 humans (73 females/111 males; age 34.5±8.8 years; percentage body fat: 31.6±8.1%), we investigated the relationship of FFM index (FFMI, kg m(-2)), FM index (FMI, kg m(-2)); and 24-h energy expenditure (EE, n=127) with ad-libitum food intake using a 3-day vending machine paradigm. Mean daily calories (CAL) and macronutrient intake (PRO, CHO, FAT) were determined and used to calculate the relative caloric contribution of each (%PRO, %CHO, %FAT) and percent of caloric intake over weight maintaining energy needs (%WMENs).
  
  
  RESULTS
  FFMI was positively associated with CAL (P<0.0001), PRO (P=0.0001), CHO (P=0.0075) and FAT (P<0.0001). This remained significant after adjusting for FMI. Total EE predicted CAL and macronutrient intake (all P<0.0001). FMI was positively associated with CAL (P=0.019), PRO (P=0.025) and FAT (P=0.0008). In models with both FFMI and FMI, FMI was negatively associated with CAL (P=0.019) and PRO (P=0.033). Both FFMI and FMI were negatively associated with %CHO and positively associated with %FAT (all P<0.001). EE and FFMI (adjusted for FMI) were positively (EE P=0.0085; FFMI P=0.0018) and FMI negatively (P=0.0018; adjusted for FFMI) associated with %WMEN.
  
  
  CONCLUSIONS
  Food and macronutrient intake are predicted by FFMI and to a lesser degree by FMI. FFM and FM may have opposing effects on energy homeostasis.
authors.affiliation: Klinik und Poliklinik für Neurologie, Universität Leipzig, Leipzig, Germany.
authors.forename: C M
authors.initials: CM
authors.lastname: Weise
authors.affiliation: Obesity and Diabetes Clinical Research Section, NIDDK-NIH, DHHS, Phoenix, AZ, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Hohenadel
authors.affiliation: Obesity and Diabetes Clinical Research Section, NIDDK-NIH, DHHS, Phoenix, AZ, USA.
authors.forename: J
authors.initials: J
authors.lastname: Krakoff
authors.affiliation: Obesity and Diabetes Clinical Research Section, NIDDK-NIH, DHHS, Phoenix, AZ, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Votruba
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight; D004041:Dietary Fats / Q000008:administration & dosage; D004043:Dietary Fiber / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D005951:Glucose Tolerance Test; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests
chemical_list: D004041:Dietary Fats; D004043:Dietary Fiber; D004044:Dietary Proteins