title: High protein diets do not attenuate decrements in testosterone and IGF-I during energy deficit.
abstract: OBJECTIVE
  Energy deficit (ED) diminishes fat-free mass (FFM) with concomitant reductions in anabolic hormone secretion. A modest increase in protein to recommended dietary allowance (RDA) levels during ED minimally attenuates decrements in insulin-like growth factor-I (IGF-I). The impact of dietary protein above the RDA on circulating anabolic hormones and their relationships with FFM in response to ED are not well described.
  
  
  METHODS
  Thirty-three adults were assigned diets providing protein at 0.8 (RDA), 1.6 (2×-RDA), and 2.4 (3×-RDA) g/kg/d for 31days. Testosterone, sex-hormone binding globulin (SHBG) and IGF-I system components were assessed after a 10-day period of weight-maintenance (WM) and after a 21-day period of ED (40%) achieved by an increase in energy expenditure and decreased energy intake. Associations between the change in FFM and anabolic hormone levels were determined.
  
  
  RESULTS
  As compared to WM and regardless of dietary protein intake, total and free testosterone, total IGF-I, and acid-labile subunit decreased (P<0.05), whereas SHBG and IGF binding proteins-1, -2, and -3 increased (P<0.05) during ED. There were no energy-by-protein interactions on any hormones or IGF-I system components measured. Changes in FFM in response to ED were negatively associated with acid-labile subunit (ALS) (r=-0.62, P<0.05) in 2×-RDA; however, no other relationships were observed.
  
  
  CONCLUSIONS
  Consuming a high protein diet does not impact the androgenic and IGF-I system response to ED. These data suggest that the protective effects of high protein diets on FFM during ED are likely not influenced by anabolic hormone concentrations.
authors.affiliation: Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Henning
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Margolis
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: McClung
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young
authors.affiliation: Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA. Electronic address: stefan.pasiakos@us.army.mil.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
mesh_terms: D000328:Adult; D031204:Caloric Restriction; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D012737:Sex Factors; D013739:Testosterone / Q000097:blood*; D015431:Weight Loss; D055815:Young Adult
chemical_list: D004044:Dietary Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I
keywords: Anabolic hormones; Androgen; Weight loss