Men with low-fat diet may suffer from lower testosterone levels

Adherence to a low-fat diet is associated with lower serum testosterone levels among men even when controlling for comorbidities, age, body mass index (BMI) and activity levels, according to a US study.

“As differences in serum testosterone between the diets were modest, the avoidance of fat restrictive diets should be weighed against the potential benefits on an individual basis,” the researchers said.

A total of 3,128 men were included in the study, of whom 457 (14.6 percent) and 764 (24.4 percent) adhered to a low-fat and a Mediterranean diet, respectively. Only two men (<0.1 percent) met the criteria for a low-carbohydrate diet, and they were excluded from further analysis.

Participants had a mean serum testosterone level of 435.5±6.7 ng/dl. Those who adhered to a low-fat diet (410.8±8.1 vs 443.5±7.3; p=0.005) and a Mediterranean diet (412.9±9.1 vs 443.5±7.3; p=0.002) had significantly lower mean testosterone. [J Urol 2020;203:398-404]

In multivariable analysis controlling for age, BMI, activity levels, diabetes, comorbidities and prostate cancer, serum testosterone levels were higher in men with a nonrestrictive diet than those adhering to a low-fat diet (ß –57.2, 95 percent confidence interval, –105.6 to –8.8; p<0.05).

“With the recent popularity of restrictive diets in the United States it is important to examine potential benefits and unintended consequences on personal health,” the researchers said. “While dieting for weight loss will clearly help optimize cardiovascular health with corresponding reductions in lipid profiles, the effect of diet on testosterone is not well established. [N Engl J Med 2008;359:229-241]

A 1984 trial showed that low-fat diets (<25-percent caloric consumption) conferred no effect on testosterone level during a 6-week period, while a similar study in 1985 reported that even greater reductions in fat intake (<10-percent caloric consumption) along with the initiation of an exercise programme had no significant effect on testosterone. [J Steroid Biochem 1984;20:459-464; Am J Med 1985;78:23-27]

On the other hand, a 2005 study involving healthy individuals with an average BMI of 27.8 kg/m² demonstrated reduced serum testosterone for as much as 12 percent in those with fat restricted diets (<15-percent caloric consumption). [J Clin Endocrinol Metab 2005;90:3550-3559]

“The discrepancies among these studies were likely due to the heterogeneity of the analysed populations and variability in the restricted diets in the study, which made drawing population-based conclusions challenging,” the researchers explained.

The present study utilized the National Health and Nutrition Examination Survey form 1999–2000, 2003–2004 and 2011–2012, and analysed men aged 18–80 years who completed the 2-day dietary history and underwent serum testosterone testing. Diets were categorized as low-fat, low-carbohydrate, Mediterranean or nonrestrictive. The association between diet and serum testosterone was assessed using multivariable modeling.

“[F]uture prospective research is required to corroborate these findings and elucidate the mechanisms by which restrictive dieting may affect serum testosterone,” the researchers said. “However, the challenges of designing, accruing and maintaining a dietary trial make this task daunting, given the high attrition rate.”