Effects of single macronutrients on serum cortisol concentrations in normal weight men

A previous study reported that a high carbohydrate meal, in contrast to a high protein/fat meal, significantly increased cortisol concentrations in visceral obese subjects. The objective of this study was to identify effects of single macronutrients on plasma cortisol concentrations. Ten male subjects (age 27.3±7.4y, BMI 22.1±1.7kg/m(2)) were studied in a randomized crossover design on four days around lunchtime after consuming breakfast matched for daily energy requirements (DER 20%). For lunch they consumed one liter of a shake (DER 18%) containing either fat, protein or carbohydrate, with a raspberry taste and similar hedonic value (59±2mm on a 100mm VAS), using water as control. Serum cortisol concentrations were measured before lunch and during three hours following lunch. Baseline cortisol concentrations did not differ among treatments. The protein as well as the fat lunch caused a significant decrease in cortisol concentrations when compared to the carbohydrate lunch, and showed no difference from the control condition (p<0.05). The cortisol response in the protein condition (AUC=37,024±3518nmol/L min) and in the fat condition (AUC=35,977±3562nmol/L min) were significantly smaller when compared with the cortisol response in the carbohydrate condition (AUC=47,310±3667nmol/L min) (p<0.03), but did not differ from the control condition (AUC=32,784±1683nmol/L min) (Fig. 1). The cortisol response in the carbohydrate condition was significantly higher when compared with the response in the control condition (p<0.004). We conclude that cortisol concentrations decreased after protein or fat intake, which was not different from control; this decrease was prevented by carbohydrate intake.