Testosterone is the primary male sex hormone, and vital for reproductive development and function. Studies have found that low endogenous testosterone is associated with an increased risk of chronic disease, including type 2 diabetes and cardiovascular disease.
Cortisol on the other hand is biochemically opposed to testosterone, as the administration of exogenous cortisol lowers testosterone. This association is also observed in chronic disease, with higher levels being associated with increased risk of cardiovascular disease mortality.
In recent decades, research has found low-carbohydrate (LC) diets have positive health effects including: weight loss, decreased triglycerides, and increased high-density lipoprotein cholesterol.
A recently published meta-analysis by researchers from the University of Worcester, Henwick Grove, Worcester, U.K., evaluated the effects of low carbohydrate diets in the endocrine system and compared them with high-carbohydrate diets on men’s testosterone and cortisone levels.
The study included a total of 27 studies, with a total of 309 participants. The researchers found that short-term (<3 weeks) low carbohydrate diet moderately increased resting cortisol. Low carbohydrate diets resulted in much higher post-exercise cortisol after long duration exercise (more than 20 minutes).
Low carbohydrate diets had no consistent effect on resting total testosterone, however high-protein with low carbohydrate diets greatly decreased resting and post-exercise total testosterone.
The researchers concluded that resting and post-exercise cortisol increase during the first 3 weeks of a low carb diet, but return to normal afterwards. Also, post-exercise cortisol remains elevated but without showing immunosuppressive effects according to immune markers. Long-term high protein diets in combination with low carbohydrates showed increased testosterone levels which is advantageous for individuals with strength, power, or hypertrophy goals.
Joseph Whittaker, Miranda Harris. Low-carbohydrate diets and men’s cortisol and testosterone: Systematic review and meta-analysis. 2022. Nutrition and Health. https://doi.org/10.1177/02601060221083079