by Avik Chatterjee, MD, MPH

In my last blog entry, I highlighted how the high fat/low carb Inuit diet could counter-intuitively be healthy for its adherents. One of my students read the article and asked me if I knew anything about the (also) high-fat, low-carb ketogenic diet. Sometimes used as a treatment for pediatric epilepsy, the diet has also become increasingly popular not just for weight loss, but to change body composition - that is, to increase muscle mass and decrease body fat percentage. The student asked me if the ketogenic diet could do that in a safe way for a young person like him.
When I write a blog post about nutrition or mention that part of my job is to study nutrition, I often get questions about diets. But outside of clinic (and increasingly, during clinic), I’ve never been asked about a diet that prevents strokes or heart attacks or improves cardiovascular health, or even that reduces overall chances of death. And it’s increasingly rare for people to ask me about weight loss in general. At least for the people I know in person and on Facebook, the question is never “how do I protect my long-term health,” but more and more often “how do I look better.”

Decreasing body fat percentage, increasing muscle mass, improving body shape - these are the outcomes that interest many people, especially “younger” people. And I put “younger” in quotes because for more and more people - not just celebrities - attaining a certain body shape is increasingly a goal, at any age.

But scientific studies on diet usually use outcomes very far removed from appearance. The important recent study on the Mediterranean diet, which followed 7,447 people aged 55 to 80 in Spain, revealed that people eating that diet had much lower rates of heart attacks, strokes and death from cardiovascular causes. This study was so successful that it was stopped early, because the control group had significantly more cardiovascular events than the group following the Mediterranean diet. This randomized controlled study of a diet was relevant for many millions of people. But for many millions of others, choosing a diet is about appearance, not health outcomes. We need studies about diets with those people in mind.

Even those studies that look at different diets for outcomes other than disease usually only measure weight loss. Losing weight and lowering body mass index (BMI) are important, because lower BMI is associated with lower risk of death. But patients (and friends and acquaintances) will increasingly be asking about how to change body shape. Can a ketogenic diet sculpt abs? Can a Paleo diet make your pecs pop?

Since patients will be attempting diets to look better, it may be worth knowing what works and also what is safe. In my experience, the default opinion on “fad” diets like the Paleo or ketogenic diets is that they must be dangerous. But where is the evidence to support this? In fact, a randomized controlled trial of the high-protein, low-carb Atkins diet revealed improvements in cardiovascular risk factors such as HDL “good” cholesterol.

Since patients will be using them and asking whether they work and whether they are safe, we need studies that:

1)      look at body composition outcomes for popular diets;
2)      look at short-term safety of such diets;
3)      look at long-term, population-level, disease and mortality outcomes for those diets.

That way, when someone asks about a strange diet, I can answer “that’s nuts!” or “go for it!” with confidence.



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