Low-Carb Diet = Low Testosterone

High protein diets are very popular now. There is a belief among many that they must eat protein in every single meal and that they cannot have too much protein.

However, a high-protein diet may lower testosterone levels, especially if the calories from protein replace calories that would otherwise have come from carbohydrates.

Gonadotropin-releasing hormone (GnRH), which is the hormone that basically starts the whole cascade of events that eventually leads to testosterone synthesis, adjusts its pulsation rate according to the glucose levels of the body. When there’s high amount of glucose present, the hypothalamus inside our brains releases more GnRH, and thus your body synthesizes more testosterone. And when there’s low amounts of glucose present in the body, the brain releases less GnRH, which slows down testosterone synthesis.


Research consistently shows that people who exercise regularly need to eat enough carbs or their testosterone will fall while their cortisol levels rise. This is a sure-fire recipe for losing muscle and gaining fat. Incidentally, it’s also a marker for excessive training stress. In a study in Life Sciences, men who ate a high carbohydrate versus a low carbohydrate diet for 10 days had higher levels of testosterone and sex hormone binding globulin, and lower levels of cortisol.

A few years later, another study took this research a step further. This time the subjects included men and women who exercised regularly. And in addition to considering the effect of their diet on hormones, researchers put them through some performance tests. Once again, when the subjects ate a low carb diet, their testosterone (and other anabolic hormones) went down, while their cortisol went up. And, after following a low carb diet for just three days, only two of the six participants were able to complete the cycling test! Meanwhile, when following the higher carb diet for three days, all six participants were able to complete the test.

In 2010, researchers reconsidered the same question — this time in relation to intense exercise. In this particular study, subjects eating the low carb diet (where 30% of their calories came from carbs) saw a drop of 43% in their testosterone to cortisol ratio. Not good. Meanwhile, the control group (who got 60% of their calories from carbs) saw no change in their testosterone/ cortisol ratios.


That being said, protein is important, but consumption of protein shouldn’t distract you from consumption of carbs and fat. All three macronutrients have important roles to play.

How much protein is recommended? Aim to consume between 1 to 2 grams of protein per kilogram of body weight.

Thanks to smartphone technology, counting protein is fairly simple. Simply do Google searches to see how much protein is in certain food, e.g. Google “protein in chickpeas” or “protein in pumpkin seeds.” Otherwise, you can read how much protein there is on the nutrition label of most food.


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