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science nutrition <strong>blog</strong>

 By Robert Schinetsky


Research has found that low-carbohydrate diets have a number of beneficial health effects including:

  • Weight loss
  • Increased HDL ("good") cholesterol
  • Decreased triglycerides


We’ve discussed the benefits of low-carb and keto diets many times previously, but one area that has been under-researched and less discussed online is the impact of low-carb diets on testosterone.

As you know, testosterone is the primary male sex hormone, essential for reproductive development and function. It also plays a key role in mood, cognitive function, and overall health & longevity. Moreover, low testosterone levels are associated with an increased risk of chronic disease, including type 2 diabetes and cardiovascular disease.

Testosterone naturally declines as men age, but other lifestyle factors can also accelerate the decline of testosterone, including:

  • Diet
  • Body fat percentage
  • Physical activity level
  • Stress (chronic emotional, psychological, or physical stress)


Stress in particular has an interesting relationship with testosterone. Essentially, they work opposite of each other. When cortisol is sky-high, testosterone levels are low.

Whats more, the body doesnt really differentiate between the types of stress. What this means is that while exercise can be a beneficial stressor that improves muscle mass, reduces body fat, and enhances bone mineral density, excessive amounts of exercise (coupled with inadequate rest & recovery measures) can result in chronically elevated cortisol levels and depressed total testosterone.

And that brings us to the crux of today’s article -- a newly published systematic review & meta-analysis on the effects of low-carb diets on men's cortisol and testosterone.[1]

Note: For the purposes of this study, the authors classified low-carb diets as containing ≤35% carbohydrate intake. This was due to the fact that (according to the researchers) there is no consensus on what carbohydrate intake constitutes a low-carb diet.

The Study: Does protein lower testosterone

Researchers scoured eight databases, from which 27 studies were cultivated, including a total of 309 participants.

Some of the key findings of the meta-analysis include [1]:

  • Exercise-induced elevations in cortisol were greater on low-carb diets compared to higher-carb diets
  • Short-term, high-protein (>35% protein intake), low-carb diets result in significant decreases in testosterone
  • After 3 weeks on low-carb/ketogenic diets resting cortisol levels return to normal


Perhaps most interesting is the finding that moderate-protein (<35%), low-carbohydrate diets had no consistent effect on resting total testosterone, however high-protein (≥35%), low-carbohydrate diets greatly decreased resting and post-exercise total testosterone.[1]

Why Is This Important?

Its commonly believed that when you opt-in to a low-carb or ketogenic lifestyle, you can essentially eat as much protein and fat as you want.

However, based on the findings of this systematic review & meta-analysis, consuming too much protein on a low-carb or ketogenic diet may adversely affect natural testosterone levels.

Additionally, consuming too much protein may hinder the transition to a ketogenic state or temporarily kick you out of it. The reason for this is that certain amino acids are glucogenic, meaning they can be converted into glucose through gluconeogenesis.

Therefore, consuming an excessive amount of protein (even if youre avoiding carbohydrates completely) can potentially reduce how much body fat and dietary fat the body uses for energy production (i.e. less fat burning).

And throwing themselves out of ketosis and using less dietary fat and body fat for fuel

Also, dont forget the fact that based on this recent review, that high protein intakes (35% or more) on a low-carb diet negatively affect testosterone levels.

To put this into context, research shows that total testosterone for a comparably aged population to the individuals included in the meta-analysis (27 years) is 14 nmol/L.[2] Researchers noted that high-protein, low-carb diets resulted in a reduction of 5.23 nmol/L --  representing a 37% decrease in total testosterone![2]

According to the researchers, this may be due high protein intakes outpacing the urea cycle's capacity to convert nitrogen derived from amino acid catabolism into urea.[2]

Moderate protein intake (<35% protein) coupled with a low-carb diet does not have the same adverse impacts on total testosterone, though.

Researchers also note that the higher post-exercise total testosterone levels on moderate-protein, low-carb diets may indicate a greater anabolic response to exercise, which is obviously of interest to individuals looking to build muscle & strength.

This flies in the face of what many men believe about low-carb diets (they can eat all the protein they want, just dont eat the carbohydrates). This new meta-analysis shows that there is a tipping point at which more protein is not better…at least in regards to your testosterone levels.

For these reasons, ThermoHeat Fat Burning Protein was formulated with lower protein and more leucine.

More specifically, ThermoHeat Fat Burning Protein includes 6.25g of whey protein fortified with 5 grams of Leucine, which has been shown to stimulate protein synthesis equivalent to consuming 25 grams of whey protein, based on the latest scientific research![3]

ThermoHeat Fat Burning Protein also includes 3 grams of MCT to stimulate ketone production. Previous studies also note that consuming 2 grams (2g) of MCT supplementation can boost fat burning during exercise, increase post-meal thermogenesis and reduce body weight and body fat.

Also included in every serving of ThermoHeat Fat Burning Protein is:

  • 3,000mg L-Citrulline (activates nitric oxide and brown fat).
  • 1,000IU Vitamin D (enhances protein synthesis when combined with whey protein and leucine).
  • 100mg grape skin extract (contains polyphenols that enhance nitric oxide and brown fat).
  • 40mg Paradoxine Grains of Paradise extract (a thermogenic brown fat activator).
  • 5mg BioPerine (a thermogenic and brown fat activator).
  • Essential electrolytes: Potassium 750mg and magnesium 100mg (from potassium and magnesium citrate). Low-carb and ketogenic diets enhance the requirements of these essential minerals.


To up the ante on your body recomposition goals, you can also add ThermoHeat Fat Burning Protein to coffee as coffee offers a number of benefits not only in regards to activating brown adipose tissue (brown fat) enhancing, fat burning and weight loss, but also cardiometabolic health. Moreover, some research indicates that, at least in the short-term (4 weeks), caffeinated coffee can increase total testosterone and decrease both total and free estradiol, indicating that caffeine may act as an aromatase (or CYP19) inhibitor.[4]

ThermoHeat Fat Burning Protein comes in delicious chocolate fudge and vanilla cream flavors, mixes easily, and is the best keto protein powder to use on a low-carb or ketogenic diet.



©Published by Advanced Research Media, Inc. 2022

©Reprinted with permission from Advanced Research Media, Inc.


  1. Whittaker J, Harris M. Low-carbohydrate diets and men's cortisol and testosterone: Systematic review and meta-analysis. Nutr Health. 2022 Mar 7:2601060221083079. doi: 10.1177/02601060221083079. Epub ahead of print. PMID: 35254136.
  2. Kelsey, TW, Li, LQ, Mitchell, RT, et al. (2014) A validated age-related normative model for male total testosterone shows increasing variance but no decline after age 40 years. PLOS One 9(10): e109346.
  3. Churchward-Venne TA, Burd NA, Mitchell CJ, et al. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Physiol. 2012;590(11):2751-65.
Wedick, Nicole M et al. “The effects of caffeinated and decaffeinated coffee on sex hormone-binding globulin and endogenous sex hormone levels: a randomized controlled trial.” Nutrition journal vol. 11 86. 19 Oct. 2012, doi:10.1186/1475-289