Study links low fat diet to decreased testosterone in men

About half a million American men are diagnosed with testosterone deficiency every year. The diagnosis can lead to decreased energy and libido, increased body fat as well as reduced bone mineral density.

To determine how a male patient’s diet may impact their testosterone levels, researchers at the University of Chicago Medicine, Northwestern University Feinberg School of Medicine, and NorthShore University Health System conducted the study, “The Association between Popular Diets and Serum Testosterone among Men in the United States,”​ which is published in The Journal of Urology.​

Details 

The researchers analyzed diet and serum testosterone level data on more than 3,100 men using the National Health and Nutrition Examination Survey, or NHANES. To meet eligibility requirements,  the men needed to be between 18 and 80 years, have undergone serum testosterone testing, and have a full 2-day dietary history data.

The researchers placed the participants into 3 categories: low fat, Mediterranean, and low carbohydrate diets. Of the 3,128 in the analysis, 973 met the criteria for a restrictive diet, 764 adhered to a Mediterranean diet, and 457 followed a low fat diet. Just 2 met low carb criteria, which resulted in that group being excluded from the analyses.

Findings 

Results of the study suggested patients on a low fat diet were more likely to have low serum testosterone levels than patients with a nonrestrictive diet.

"We found that men who adhered to a fat-restrictive diet had lower serum testosterone than men on a nonrestrictive diet,"​ according to the report by Jake Fantus, MD, of the Section of Urology, Department of Surgery, University of Chicago Medicine. "However,"​ the researchers add, "the clinical significance of small differences in serum T across diets is unclear."​

The results suggest that diet does in fact impact total serum testosterone levels. Nearly 27% of the men analyzed had testosterone levels below 300 ng/dl (nanograms per deciliter), which is the American Urological Association’s cutoff for testosterone deficiency. 

The average serum testosterone level in the study was 435.5 ng/dL. However, men following a low-fat diet had an average T-level of 411 ng/dL, and men following a Mediterranean diet came in at 413 ng/dL.

After these initial findings, the research team refined the study by factoring in age, BMI, exercise habits, and medical history. The low-fat diet was still found to be significantly associated with decreased testosterone, while the Mediterranean diet no longer was. 

According to the authors, the best diet regimen for men with low testosterone remains unknown.  The authors note that for overweight men, the health benefits of a low-fat diet likely far exceed the small reduction in serum testosterone. On the other hand, avoiding a low-fat diet "may be a reasonable component"​ to increasing testosterone in men who are not overweight. 

Further studies needed, but unlikely 

The research team noted that further studies are necessary to corroborate their findings, and to determine how restrictive diets reduce testosterone levels. However, the authors add large-scale dietary studies are unlikely due to how difficult they are to run. 

"Therefore, our data represent a valuable approach towards answering this important question,"​ concluded the authors. 

Source:​ Journal of Urology ​

Vol 203, Issue 2, February 2020 https://doi.org/10.1097/JU.0000000000000482​

“The Association between Popular Diets and Serum Testosterone among Men in the United States” ​

Authors: R. Fantus, et al.