Keto and Testosterone: What the Studies Show
The ketogenic diet has gained attention for its potential effects on hormonal health, particularly testosterone in men. Research suggests carbohydrate restriction may influence androgen levels through several mechanisms, including improved insulin sensitivity and changes in fat metabolism. Here’s what the current evidence reveals.
How Ketosis Affects Hormones
Ketosis alters the body’s primary fuel source from glucose to ketones, which appears to impact hormone production. Studies indicate that very-low-carbohydrate diets can reduce circulating insulin levels, a hormone that inversely correlates with testosterone. Lower insulin may allow for greater free testosterone availability. Additionally, the ketogenic diet’s effect on reducing visceral fat—a known site of estrogen production—could further support androgen balance.
The Research on Testosterone
While direct studies on keto and testosterone remain limited, related research offers insights. A 2020 study in the Journal of Endocrinology found that men on low-carb diets had higher free testosterone compared to those on high-carb plans. Another trial noted improved luteinising hormone (LH) secretion, which signals the testes to produce testosterone. However, long-term effects require more investigation.
What This Means in Practice
For men considering keto to support testosterone, practical adjustments matter. Prioritising dietary fats like those in full-fat dairy (e.g., Tesco’s mature cheddar at £2.50 for 400g) and monounsaturated oils helps maintain cholesterol, a testosterone precursor. Seasonal eating—such as winter root vegetables in moderation—can provide fibre without excessive carbs. Those engaged in strength training on keto may notice enhanced recovery and performance.
Potential Caveats
Extreme caloric restriction or very low body fat percentages can temporarily suppress testosterone, regardless of diet type. Ensuring adequate intake of keto-friendly magnesium sources like pumpkin seeds is crucial, as magnesium deficiency correlates with lower testosterone. Individual responses vary, and men with existing hormonal conditions should consult a clinician.
Frequently Asked Questions
Does keto increase testosterone for all men? Not universally. While some men see rises in free testosterone on keto—especially if coming from high-carb diets—others may experience no change. Genetics, body composition, and exercise habits all play roles.
How long before testosterone changes occur? Metabolic adaptations take weeks, but hormonal shifts may begin within 1–2 months. Studies tracking testosterone specifically note changes around the 3-month mark.
Can keto lower estrogen too much? Unlikely in moderation. The diet’s fat content supports hormone synthesis. However, men with very low body fat should monitor energy intake to avoid hormonal dips.
The Bottom Line
The ketogenic diet may support testosterone levels in men through improved insulin sensitivity, reduced visceral fat, and optimized cholesterol metabolism. While not a guaranteed ‘boost’, the evidence suggests keto is at least neutral—and potentially beneficial—for androgen balance compared to high-carb diets. If you’d rather not do the macro maths yourself, the Keto Dieting app does it for you on Google Play and the App Store.
References
- Kosinski C, Jornayvaz FR (2017). Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies. Nutrients. https://doi.org/10.3390/nu9050517
- Paoli A, Rubini A, Volek JS, Grimaldi KA (2013). Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition. https://doi.org/10.1038/ejcn.2013.116
