The overall scientific literature shows that eating more fat may increase a man’s natural testosterone levels by 10-15%.

The researchers mostly studied the effects of 40% of calorie intake as fat vs. 20% [Dorgan 1996, Wang 2005, Volek 1997].

But how about pushing it even higher? 60% of calorie intake, perhaps?

This unpublished study by Zajac and colleagues (2015) did just that:

For 6 weeks, 10 powerlifters and bodybuilders ate 3200 calories with either 30% or 60% coming from fat.

The participants saw their testosterone increase a significant 15.7% after the very high fat diet. Growth hormone levels rose as well.

Additionally, their cholesterol profiles improved significantly, but it’s hard to say whether it will actually protect from certain cardiovascular diseases with the current state of research.

So there you go, although this research remains unpublished, it hints at a possible advantage of keto (or very high fat) diets when it comes to a hormonal milieu for growing more muscle.

If you’ve become curious about ketogenic (high fat) dieting: I highly recommend Ketogains as a coaching and science-based information source.