Powerlifting Bench Press

Testosterone and Cortisol in Relationship to Dietary Nutrients and Resistance Exercise

Volek et al (1) examined the effects of  diet on pre and post-exercise blood concentrations of  testosterone and cortisol.  They measured hormonal  concentrations in 12 trained men and then had them  participate in a resistance exercise protocol consisting  of 5 sets of 10 RM on bench press and 5 sets of 10  repetitions of squat jumps using 30% 1 RM squat.  They  then measured hormonal concentrations 5 minutes after the  training session.  Subjects also completed 17 days  of detailed food intake prior to the study.

FINDINGS:  No effect of diet was  found on pre-exercise concentrations in cortisol or  absolute increases in testosterone caused by the  resistance training session.  A significant effect  of diet on pre-exercise testosterone levels was found,  however.  A significant negative correlation was  found between testosterone concentration and percentage  of calories from protein intake, the polyunsaturated-to-saturated  fat ratio, and the protein-to-carbohydrate ratio.  A  significant positive correlation was found between  testosterone concentration and percentage of calories  from fat intake, total grams of saturated fatty acids,  and total grams of monounsaturated fatty acids.

IMPLICATIONS:  Diet may have a  significant effect on blood concentrations of  testosterone.  A higher percentage of calories from  protein may reduce blood concentrations of testosterone,  and a higher percentage of calories from fat, saturated  fat, and monounsaturated fat may result in higher blood  concentrations of testosterone.  Extremely low fat  diets (such as around 10% of calories) or extremely high  protein diets may actually be detrimental to testosterone  levels which could possibly have a detrimental effect on  muscle mass gains.  

One must be cautious when interpreting  these findings, however.  Diets were recorded by the  subjects and not controlled by the researchers, possibly  reducing the accuracy of the records.  In addition,  the findings of this study are purely correlational;   whether a cause-effect relationship exists between  diet and blood concentration of testosterone and whether  it has any effect on strength and muscle mass gains  remains to be determined.  More research is  warranted.

1.  Volek, J.S., W.J. Kraemer, J.A.  Bush, T. Incledon, and M. Boetes.  Testosterone and  cortisol in relationship to dietary nutrients and  resistance exercise.   J. Appl. Physiol.  82(1):49-54.   1997.