High protein diets do not attenuate decrements in testosterone and IGF-I during energy deficit

Metabolism. 2014 May;63(5):628-32. doi: 10.1016/j.metabol.2014.02.007. Epub 2014 Feb 17.


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.

Materials/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.

Conclusion: 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.

Trial registration: ClinicalTrials.gov NCT01292395.

Keywords: Anabolic hormones; Androgen; Weight loss.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Caloric Restriction*
  • Diet
  • Dietary Proteins / administration & dosage*
  • Energy Metabolism*
  • Female
  • Humans
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Sex Factors
  • Testosterone / blood*
  • Weight Loss*
  • Young Adult


  • Dietary Proteins
  • Testosterone
  • Insulin-Like Growth Factor I

Associated data

  • ClinicalTrials.gov/NCT01292395