The class of hormones collectively called steroid hormones, which includes testosterone, oestrogen, progesterone, DHEA, cortisol, and aldosterone, are all derived from cholesterol. The liver produces approximately 75 percent of the body's cholesterol endogenously, with the remaining 25 percent coming from dietary sources. Very low fat diets reduce circulating cholesterol and consistently produce lower steroid hormone concentrations across multiple clinical trials.
The Low-Fat Diet and Hormone Decline
A six-week crossover study comparing high-fat and low-fat diets in men found that total testosterone was 15 percent lower on the low-fat diet. Subsequent meta-analyses have confirmed this finding: low-fat dietary periods consistently produce lower total and free testosterone than moderate-fat or high-fat dietary periods. For adults over 35 who are already experiencing age-related androgen decline, adopting a very low-fat diet compounds this natural decline through a second, entirely dietary mechanism.
Which Fats Support Hormone Production
The fats that best support steroid hormone production are saturated and monounsaturated fats from whole food sources. Research consistently shows positive correlations between intake of egg yolks, full-fat dairy, olive oil, and avocado and circulating testosterone levels. Polyunsaturated fats, particularly the high-omega-6 linoleic acid from refined vegetable oils, show less consistent or negative associations with testosterone in some studies, possibly through effects on steroidogenesis enzymes.