Adherence to low-fat diet may lead to lower serum testosterone in men

USA: Men who adhere to a low-fat diet have lower serum testosterone than men on a nonrestrictive diet, finds a recent study in the Journal of Urology. However, the clinical significance of small differences in serum T across diets is unclear.

According to the study, in overweight or obese men, the health benefits of a low-fat diet likely far exceed the small reduction in serum testosterone. In contrast, for men who are not overweight, avoiding a low-fat diet "may be a reasonable component" of a multifaceted approach to increase serum testosterone.

Low testosterone is highly prevalent in the United States, as approximately 500,000 men are diagnosed with testosterone deficiency each year. Testosterone deficiency can lead to problems, including decreased energy and libido, along with physiological alterations, including increased body fat and reduced bone mineral density.

In addition to medications, treatment for low testosterone often includes lifestyle modifications, such as exercise and weight loss. But the effects of diet on testosterone levels have been unclear. Because testosterone is a steroid hormone derived from cholesterol, changes in fat intake could alter testosterone levels. This new analysis of how diet affects serum testosterone provides evidence that a low-fat diet is associated with lower testosterone levels, compared to an unrestricted diet.

For the many men diagnosed with testosterone deficiency, losing weight can help increase testosterone levels. But certain diets - specifically a low-fat diet - may be associated with a small but significant reduction in testosterone.

Richard J. Fantus, Department of Surgery, NorthShore University Health System, Evanston, Illinois, and colleagues examined the relationship of the serum testosterone level to low fat, Mediterranean and low carbohydrate diets in a large, nationally representative patient sample.

For the purpose, the researchers analyzed data on 3,128 men from a nationwide health study (the National Health and Nutrition Examination Survey, or NHANES). All participants had available data on diet and serum testosterone levels.

Key findings of the study include:

• Of the 3,128 men who met study inclusion criteria 457 (14.6%) and 764 (24.4%) met the criteria for a low-fat and a Mediterranean diet, respectively.


• Only 2 men (less than 0.1%) met the criteria for a low carbohydrate diet, which was removed from further analysis.


• Mean ± SD serum testosterone was 435.5 ± 6.7 ng/dl.


• Mean testosterone was lower among men with a low-fat diet (410.8 ± 8.1 vs 443.5 ± 7.3) and a Mediterranean diet (412.9 ± 9.1 vs 443.5 ± 7.3).


• Multivariable analysis controlling for age, body mass index, activity level, diabetes, comorbidities, and prostate cancer showed that men with a nonrestrictive diet had higher serum testosterone than those adhering to a low-fat diet (ß –57.2).

"Further studies will be needed to corroborate their findings and to clarify the mechanism by which restrictive diets reduce testosterone. But due to the difficulties of large-scale dietary studies, definitive trials are unlikely to be performed. Therefore, our data represent a valuable approach towards answering this important question," the authors conclude.

The study, "The Association between Popular Diets and Serum Testosterone among Men in the United States," is published in the Journal of Urology.

DOI: https://doi.org/10.1097/JU.0000000000000482