It is trendy for biohackers to adopt a low carb diet choosing to fuel themselves on ketones rather than glucose. Testosterone levels can take a hit during long term carbohydrate restriction or fasting. I start to suspect something is up if I haven’t felt a need to shave in the last three days. The longevity forum has a good thread discussing natural ways to stabilize, recover and increase testosterone with linked studies.

Via longecity forum:

Increases T above baseline

• ginger, 10g (+17.7%, unknown mechanism) [1]
• intense exercise, squat (+15.1%) [2]
• high saturated and monounsaturated fat (low fiber and polyunsaturated fat) [2b]
• DHEA, 200mg (found in wild yams, precursor)
• ginkgo [3]

Only normalizes deficiencies

• tribulus [1]
• zinc (oysters) [2]
  • deficiencies in other minerals may affect T levels
• vitamin d2 (irradiated mushrooms)