How Much Fat Should We Have in Our Diet?

What we do and don’t know

Dr. David L. Katz
Heated
Published in
4 min readJan 30, 2020

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Photo: Morten Falch Sortland/Getty Images

Even as the public health community wages a high-profile battle over how much processed meat it’s safe to eat, the community of vegan or plant-based nutrition experts has been waging a war of its own over the role of fat and its various sources in a plant-based diet.

One camp contends that the optimal plant-based diet is made up preferentially of whole foods, but must also be low in total fat, period. For this group, almonds, walnuts, and avocados are off the menu.

Another camp maintains that higher-fat foods are fine, provided they are plants and limited to whole foods. So here, walnuts and avocados are acceptable, but extra-virgin olive oil — and any other extracted oil, for that matter — still comes with a skull and crossbones.

And finally, there is the faction that allows for “good” extracted oils, such as extra-virgin olive oil, along with good, natively high-fat, whole foods.

These differences might be minor. But alas, the civil capacity to agree about disagreeing, to differentiate shared facts from divergent opinions, is a victim of the social-media age.

We are all entitled to our own opinions, but we are not entitled to our own facts. Our topline question should be: What do we know, and what is just opinion or preference? Content experts, to qualify as such, should reliably make the distinction. All too often, it gets cooked as rhetoric gets overheated.

The most restrictive diet — whole-food predominant, plant-exclusive, low in total fat (less than 10 percent of calories), and thus exclusive of both high-fat whole foods (nuts, seeds, olives, and avocados) and any extracted oil — can do great things for health. Such a diet has been shown to cause regression of atherosclerotic plaque.

But that very evidence, impressive as it may be, is where distinctions between what is known and what is simply favored begin to fall apart. There is a famous expression from the realm of logic: Absence of evidence is not evidence of absence.

That’s pretty much the state of the science regarding dietary fat content and coronary plaque. Studies using higher-fat diets, notably a Mediterranean diet in the Lyon Diet Heart Study

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Dr. David L. Katz
Heated

President, True Health Initiative; CEO, Diet ID; Founder, Former Director, Yale-Griffin Prevention Research Center. @DrDavidKatz