Low-fat diets and testosterone in men: Systematic review and meta-analysis of intervention studies.

Plain-language summary

This study set out to see what happens to a man's testosterone when he cuts fat out of his diet, at a time when levels have been falling across Western countries. It pooled six intervention studies covering 206 men, each comparing a lower fat diet against a higher fat one, and measured several sex hormones. Low fat diets were followed by small but consistent drops in total testosterone, free testosterone, testosterone measured in urine, and dihydrotestosterone (DHT, a stronger form of testosterone the body makes from it in tissues such as skin and the prostate). The drop was larger in men of European descent. Luteinizing hormone (the pituitary signal that tells the testicles to make testosterone, so less of it means less signal) and sex hormone-binding globulin (SHBG, a protein that binds testosterone and sets how much is free and usable, so a higher level leaves less available) did not move. The paper reports how much testosterone changed and not what the men's average levels actually were on either diet, so there is no before and after number to put on it.

Key findings

• Low fat diets were followed by a small but consistent fall in total testosterone.
• Free testosterone, testosterone measured in urine and dihydrotestosterone fell as well.
• The fall was larger in men of European and North American descent.
• For luteinizing hormone and sex hormone-binding globulin, no relationship was found. Neither moved.
• The paper does not report absolute average testosterone levels for the low fat and high fat periods, only the size of the change between them.