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Plasma cortisol response to exercise‐induced negative energy balance is affected by protein intake
Author(s) -
Karl James Philip,
Smith Tracey J,
Pikosky Matthew A,
Mathow Mona M,
Glickman Ellen L,
Grediagin Ann,
Young Andrew J
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb26-c
Subject(s) - medicine , endocrinology , basal (medicine) , energy expenditure , energy balance , chemistry , zoology , biology , insulin , ecology
A multi‐stressor environment including restricted energy intake (EI) and increased energy expenditure (EE) has been shown to cause increases in serum cortisol in trained men. It is unclear if this response can be influenced by dietary macronutrient content. This study examined the affect of protein intake on the basal plasma cortisol (C) response to an exercise‐induced energy deficit. Twenty‐one males (23 ± 5 yrs; 78 ± 9 kg; VO 2peak 59 ± 9 ml·kg −1 ·m −1 ) consumed a diet containing 55% ± 1% carbohydrate and either 0.9 or 1.8 g protein/kg body weight for 11 days. Following 4 days of energy balance (EB), EE was increased 1000 kcal/d for 7 days by exercise at 50–65% VO 2peak . Seven volunteers remained in EB and consumed a moderate protein diet (B‐MP). Fourteen volunteers sustained a 1000 kcal/d energy deficit while consuming either a moderate (D‐MP) or high (D‐HP) protein diet. EE was periodically measured during rest and exercise using open‐circuit spirometry. Fasting blood samples were obtained on days 5, 6, and 11 and C levels measured. Average daily energy deficit of D‐MP and D‐HP was not different (868 ± 170 kcals and 1006 ± 86 kcals, respectively). Fasting C increased from day 5 to day 6 (15.7 ± 2.4 to 17.8 ± 2.3 ug/dl; p<0.05) and from day 5 to day 11 (15.7 ± 2.4 to 17.5 ± 2.8 ug/dl; p<0.05) in D‐MP, but remained unchanged in B‐MP and D‐HP. A sustained increase in physical activity over several days resulted in an increase in C when EI was not adjusted to maintain EB, suggesting that energy deficit induced proteolysis. A high protein intake appears to attenuate this response. Research funded by MRMC.