We’ve written before about the ketogenic diet:

Ketogenic Diet: Burning Fat Or Burning Out?

…and the answer to the question posed by that title is “both”:

• the one thing that it is generally considered good for (aside from managing refractory epilepsy in children, which is what the diet was originally designed for) is fat loss
• however, this comes at the cost of cumulative health issues, mostly for the heart, which risks thus become more dangerous over time, for example:

❝As obesity rates in the populace keep rising, dietary fads such as the ketogenic diet are gaining traction.

Although they could help with weight loss, this study had a notable observation of severe hypercholesterolemia and increased risk of atherosclerotic cardiovascular disease among the ketogenic diet participants.❞

~ Dr. Shadan Khdher et al.

Read in full: The Significant Impact of High-Fat, Low-Carbohydrate Ketogenic Diet on Serum Lipid Profile and Atherosclerotic Cardiovascular Disease Risk in Overweight and Obese Adults

…although there are other problems too, for example: Is Losing Weight Worth Losing Your Kidney: Keto Diet Resulting in Renal Failure

Nevertheless, let’s take a look at that fat loss for which so many people turn to keto:

Ketogenic diet and sex differences

Like most health science for anything outside of “the bikini zone” (i.e. places covered by a bikini), most research into the ketogenic diet has not taken sex differences into account, and has typically looked at either male participants, or participants of any sex and/but without those sex differences being looked at.

However, “most” is not “all”, and a team of researchers (Dr. Yingying Jiao et al.) did examine those sex differences.

She and her team found that over the same period of time, men lost 11.63% of body weight vs 8.95% for women on identical ketogenic diet protocols.

Grabbing a calculator (100(11.63-8.95)/11.63), we see that that means 23% less weight loss for women.

You can read the paper in full, here: Sex differences in ketogenic diet: are men more likely than women to lose weight?

As to why, it comes down to several factors, but first, let’s do a quick recap of how the ketogenic diet works for fat loss: it’s an extremely low-carb, moderate-protein, high-fat diet that mimics fasting. In response to this, the body shifts from using glucose for energy to using ketones. This promotes fat breakdown, reduces appetite, and maintains blood glucose levels as it goes.

Now, let’s look at the process piece by piece.

In terms of hormone signalling:

• estrogen conserves fat breakdown via α-adrenergic receptors
• testosterone accelerates fat breakdown by increasing β-adrenergic receptors

In terms of metabolic energy use:

• estrogen promotes the storage fatty acids as triglycerides and use of carbs as energy
• testosterone promotes the oxidization of fatty acids for energy and store carbs

In terms of where body fat is stored (and thus how easy it is for the body to get at it):

• estrogen promotes the storage of fat subcutaneously (harder to mobilize)
• testosterone promotes the storage of fat viscerally (easier to burn)

In short, everything estrogen does in this regard improves our endurance and helps us survive famine.

Which, on an evolutionary level, is fabulous. However, when it comes to trying to use fasting (or, as in the case of keto, a fast-mimicking diet) to lose weight, then it isn’t so helpful.

Our body is just too well-prepared for it and responds to the “famine” (extremely low-carb diet) by going “don’t worry, we’ve got this!” and carefully rationing our body fat to ensure we can survive the winter.

You may be wondering: if all this is about estrogen vs testosterone, then does untreated menopause (and thus much lower estrogen levels) change this?

And the answer is: yes, it does, albeit not completely, because testosterone levels will still not be so high as in men. Thus, in the category of fat loss, the ketogenic diet:

• works well for men,
• works moderately well for women in untreated menopause, and
• works least well for premenopausal women and women on HRT.

(This is all discussed in the above-linked paper too, by the way)

On that latter note (the menopause etc), it’s also worth bearing in mind that an extra concern that typically comes with the menopause anyway, is further compounded in the case of conforming to a ketogenic diet, because even in the short term, keto already increases osteoporosis risk:

❝Markers of bone modeling/remodeling were impaired after short-term low-carbohydrate high-fat diet, and only one marker of resorption recovered after acute carbohydrate restoration❞

~ Dr. Ida Heikura et al.

A Short-Term Ketogenic Diet Impairs Markers of Bone Health in Response to Exercise

If you, dear reader, are a woman and perhaps of a certain age, and all this has prompted you to wonder what dietary balance (especially: ratio of energy from fat to energy from carbs) might be better for you, then this is quite personalizable, so check out:

What Macronutrient Balance Is Right For You?

Want to lose weight, but not on keto?

We’ve got you covered:

How To Lose Weight (Healthily!)

Want to learn more?

For more on sex differences in nutrition (and exercise), with a focus on what’s best with female physiology, you might like this very good book that we reviewed recently:

ROAR: Match Your Food and Fitness to Your Unique Female Physiology for Great Health, Optimum Performance, and a Strong Body for Life – by Dr. Stacy Sims

Enjoy!