Protein ingestion prior to strength exercise affects blood hormones and metabolism

Med Sci Sports Exerc. 2005 Nov;37(11):1990-7. doi: 10.1249/01.mss.0000175912.64126.f9.


Purpose: The effects of protein consumption before strength training session on blood hormones, energy metabolites, RER, and excess postexercise oxygen consumption (EPOC) were examined.

Methods: Ten resistance-trained young men consumed either a 25 g of whey and caseinate proteins (PROT) or a noncaloric placebo (P) in a liquid form 30 min before a heavy strength training session (STS) in a crossover design separated by at least 7 d. STS lasted 50 min and included 5 x 1 RM squats, 3 x 10 RM squats and 4 x 10 RM leg presses with 2-, 3-, and 2-min recoveries, respectively. A protein-carbohydrate supplement was consumed after STS in both trials. Venous blood samples were collected before, during, and after STS and oxygen consumption before and after STS.

Results: Serum growth hormone (GH), testosterone, and free fatty acids (FFA) were significantly (P < or = 0.05) higher in P compared with PROT 5 min after an STS. The calculated area under curve (AUC) of the serum insulin response during an STS was significantly (P < 0.001) higher in PROT compared with P. The EPOC value from 90 to 120 min after an STS was significantly greater in the PROT condition compared with P (P = 0.01), and PROT treatment had a significantly higher RER 2 h postexercise (P = 0.04). The AUC of serum FFA during STS correlated significantly and negatively with RER 10-30 min after STS (r = -0.53, P = 0.02).

Conclusions: Consuming 25 g of whey and caseinate proteins 30 min before an STS significantly decreases serum GH, testosterone, and FFA levels, and increases serum insulin during an STS. Furthermore, the pre-STS protein increased EPOC and RER significantly during 2-h recovery after STS.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Area Under Curve
  • Cross-Over Studies
  • Dietary Proteins / metabolism*
  • Fatty Acids / blood
  • Fatty Acids / metabolism*
  • Human Growth Hormone / blood
  • Humans
  • Insulin / blood
  • Male
  • Milk Proteins / metabolism
  • Oxidation-Reduction
  • Oxygen Consumption
  • Placebos
  • Testosterone / blood*
  • Time Factors
  • Weight Lifting / physiology*
  • Whey Proteins


  • Dietary Proteins
  • Fatty Acids
  • Insulin
  • Milk Proteins
  • Placebos
  • Whey Proteins
  • Human Growth Hormone
  • Testosterone