Is Keto Better Than The Mediterranean Diet For Metabolic Health?

Science has questions, and science has answers:

The big picture

The study that made some headlines compared three diets in 55 adults with a BMI category of “obese”, of whom 42 completed the study, with an average age of 43 and a mixture of men and women. All finishing participants lost approximately 10% of their body weight over approximately 5 months, allowing researchers to examine the effects of diet composition independently of weight loss.

The diets:

• The very low-carbohydrate ketogenic diet provided less than 20g of carbohydrates daily (4% of calories), 23% protein, and 73% fat
• The Mediterranean diet provided 254g of carbohydrates (50%), 15% protein, and 35% fat
• The low-fat plant-based diet provided 352g of carbohydrates (70%), 15% protein, and 15% fat

However! This means that the trial compared a very low-carbohydrate diet with two high-carbohydrate diets, rather than including a low-to-moderate-carbohydrate option, and protein intake wasn’t matched across all groups, making it harder to isolate the effects of carbohydrates and fats alone.

In terms of results, all three groups achieved the same 10% weight loss; the Mediterranean diet showed trends towards greater reductions in LDL cholesterol, ApoB, and systolic blood pressure, but none were statistically significant, while fasting triglycerides decreased more with keto, although 24-hour triglyceride levels weren’t significantly different between diets.

Where there was more difference was in insulin sensitivity and liver fat: muscle insulin sensitivity improved in all three groups, while liver insulin sensitivity improved by 67% with keto compared with 47% with both the Mediterranean and plant-based diets; liver fat also decreased in all groups, with the greatest reduction in the ketogenic group.

This is interesting, because despite concerns that ketogenic diets can increase LDL cholesterol and insulin resistance through high saturated-fat intake, neither occurred in this study, partly because most of the additional fat consumed by the keto group was unsaturated rather than saturated, which is simply often not the case in reality.

So, a blanket claim would become more than a bit irresponsible.

This also further blurs the results, because replacing saturated fat with unsaturated fat reduces coronary heart disease risk, as does replacing saturated fat with complex carbohydrates, but replacing it with refined carbohydrates doesn’t provide the same benefit; therefore, regardless of carbohydrate and fat proportions, prioritize unsaturated fats and high-fiber complex carbohydrates.

Lastly, it’s important to keep in mind that the Mediterranean diet has substantial evidence supporting reductions in long-term health outcomes, including heart attacks and type 2 diabetes, whereas evidence on the long-term effects of keto is limited and maintaining extremely low carbohydrate intake can be difficult; the one-year DIETFITS trial also demonstrated that participants gradually increased their carbohydrate intake on the low-carb diet and fat intake on the low-fat diet when preparing their own food.

So, in summary: no, the study doesn’t justify ditching carbohydrates or declaring keto the best diet; it provides interesting evidence about short-term improvements in liver metabolism, but longer studies are needed to compare moderate low-carbohydrate diets, ketogenic diets, and transitions from keto to sustainable maintenance diets (bearing in mind, keto is not at all sustainable, if by “sustainable” we mean without increasing health risks).

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Take care!