Should You Eat a High-Fat Diet for a Low-Fat Body?

The nutrition myth buster Jonny Bowden explains the slimming power of a high-fat diet.
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To learn more about high-fat diets, see How We Got the Fat Thing All Wrong

High-fat diets are making a comeback.

If you just blinked your eyes real fast when you read that sentence, you’re hardly alone. Recently, I was asked by a reporter to describe a healthy diet. I mentioned that I personally – for my own health – like a diet high in fat. But when the reporter filed the story, he quoted me as saying that I recommended a diet low in fat. He had never heard a nutritionist recommend a high-fat diet before; what I said was so foreign to his ears that he just assumed he had misunderstood. (He wrote what he expected I would say, rather than what I actually said.) 

Get used to it, Mr. Not-Very-Good Reporter. Several high-profile docs are releasing books this year that promote higher-fat diets as a way of balancing hormones, promoting cardiovascular and brain health, preventing diabetes and, oh yes, losing weight. Especially losing weight. (More on that in a moment.) Turning 40 years of dietary advice on its ear, the current crop of diet books are advocating a recipe for weight loss that is almost unheard of: They’re telling us to eat more fat, not less.

Are they crazy? Not exactly.

Full disclosure: I’m one of those authors. Writing with Steven Masley, MD, a fellow with the American Heart Association and clinical assistant professor at University of South Florida, I recently published a book called Smart Fat: Eat More Fat. Lose More Weight. Get Healthy Now. (HarperOne, 2016) But I’m hardly the only one talking about high-fat diets. This year, Mark Hyman, MD, who is the Clintons’ doctor as well as the director of the Cleveland Clinic Center for Functional Medicine, released Eat Fat, Get Thin (Little, Brown and Company, 2016). The “First Lady of Nutrition,” Ann Louise Gittleman, PhD, CNS, also recently released an updated version of her classic Eat Fat, Lose Weight (Blue Hills Publishing, 2015). 

And that’s just the beginning. The esteemed endocrinologist and Harvard Medical School professor David Ludwig, MD, PhD, just released a superb book, Always Hungry? (Grand Central Publishing, 2016), which pretty much buries low-fat dogma once and for all and supports a diet higher in fat along with proteins, whole grains and starchy vegetables.

So, what’s going on? 

Let’s start with the crumbling of a couple of myths that the dietary establishment has accepted as gospel for the last 40 years. The first is that weight loss is all about cutting calories. The second is that all calories are created equal.

Both assumptions turned out to be stunningly wrong.

If all calories are equal (a calorie equals a calorie no matter where it comes from), and if weight loss is accomplished by cutting calories – and if those were the only things to consider – then sure, it makes sense to cut out fat. Gram for gram, fat has more than twice as many calories as carbs and protein. So, like an accountant trimming the budget, we cut out the most calorically “expensive” item on the menu: dietary fat.

It was a simplistic and shortsighted solution. Fats help balance our hormones. They make certain vitamins (A, D, E, K) and other compounds like carotenoids absorbable. They’re the parent molecules for all kinds of important hormones and mini-hormones known as eicosanoids. And, because of their lack of effect on insulin (the fat-storage hormone), adding more fat to your diet, while at the same time reducing carbs, makes weight loss a heck of a lot easier. 

Meanwhile, the best thinkers in nutrition these days are rethinking the primacy of calories in the weight-loss equation and looking instead to see how those calories affect hormones. Calories from sushi are processed differently than calories from broccoli or, for that matter, butter or candy or apple juice, or just about any food you can name. The old notion of “a calorie is a calorie” is just no longer tenable. Food has a hormonal effect, and hormones, after all, run the show when it comes to fat loss (and fat gain). 

It’s actually because of the hormonal effect of food that high-fat diets are making a comeback. And the hormone that’s center stage in the fat-loss drama is insulin, which the pancreas secretes whenever blood sugar rises. Insulin’s job is to get rid of sugar in the bloodstream and escort it into the muscle cells to be used as fuel. 

When most people eat the conventional American high-carb, low-fat diet, their blood sugar will elevate frequently and it will go high, causing a lot of insulin to be released. Remember, insulin is the fat-storage hormone, not the fat-releasing hormone. When insulin is high, the fat cells lock their doors and won’t release their goodies. You wind up relying on more sugar and starch for energy because your fat can’t be burned for fuel. It’s like having a huge bank account, but you don’t have the code for the ATM card – so you can’t access your fortune.

The food group that has the greatest and most profound effect on insulin is – you guessed it – carbohydrates. Protein has a moderate effect; it doesn’t compare to the effect of carbs, but it’s still there nonetheless. 

Guess what has no effect on insulin. Fat.

Think about the absurdity of the health establishment recommending a weight-loss diet high in the food group most likely to raise fat-storing hormones (carbohydrates) while low in the food group that has virtually zero effect on that hormone (fats). It’s just breathtakingly wrong.

One of the many benefits of fat is energy. Fat produces more energy per gram than any other food group. You want to be burning fat. After all, your body can only store about 1,400 to 1,800 calories as sugar (either as glucose or glycogen). But it has a virtually unlimited storage capacity when it comes to storing calories as fat! Fat’s your best energy source, but most people aren’t able to use their body-fat stores effectively because the food we’re eating locks them up. So it sits there, taunting us, on our waist, hips, belly and thighs, while we reach for another bagel to fuel our tired bodies.

Hence the rebirth of high-fat diets.

High-fat diets – also known as ketogenic diets, for reasons I’ll explain in a minute – have been used for weight loss since at least 1851 when William Banting published what was probably the very first international best-selling diet book, A Letter on Corpulence. But ketogenic diets didn’t get really popular until the publication of Dr. Atkins’ New Diet Revolution by Robert Atkins, MD, in 1972. 

Atkins advocated a diet very low in carbs (20 grams a day or less) because when you eat so few carbs, your body will almost invariably switch fuel sources. Instead of primarily burning sugar, it’s now forced to burn fat. With so little sugar in the diet, the body begins to cannibalize its own storage sites (fat tissue), break down the fat and use the by-products of this breakdown for fuel.

The by-products of that fat metabolism are called ketone bodies, and that’s why very-low-carb, high-fat diets are called “ketogenic” diets. Ketone bodies (or ketones) make a very tasty fuel source for the body. By some accounts, they’re an even better fuel than sugar – especially for the heart and brain. Ketogenic diets had a bad rap in conventional medical circles for a very long time because doctors, not trained in nutrition, confused the nutritional ketosis that Atkins advocated with the life-threatening condition of diabetic ketoacidosis.

But these high-fat, ketogenic diets are making quite a comeback these days and they’ve expanded their résumé way beyond weight loss. They’re used so commonly as a treatment for childhood epilepsy that hospitals typically lose points in evaluation metrics when they don’t offer it. More and more high-performance athletes are experimenting with them. Wiry, athletic health professionals and researchers like former powerlifter Jeff Volek, PhD, RD, of The Ohio State University and physician-scientist Stephen Phinney, MD, PhD, swear by them. So does the great integrative medical neurologist and author of Grain Brain (Little, Brown and Company, 2013), David Perlmutter, MD. I recently attended a conference at The University of Tampa in which presentations were given showing how and why the navy is testing these diets for possible special forces applications. 

Ketogenic diets are notoriously difficult to stick with, and not everyone can do them. Fortunately, it’s not necessary to be in nutritional ketosis to get the awesome benefits of smart fats. You just have to include more smart fats in your diet while at the same time including fewer of the ingredients that make us fat, sick, tired and depressed.

Here’s the truth.

Some fats are terrible for you, some are wonderful for you, and some are, well, neutral. But the old division of “good fat” and “bad fat” didn’t go deep enough. It was a crude categorization that stuck any food high in saturated fat (meat, butter, coconut oil) in the “bad” category and any food of non-animal origin (soybean oil, canola oil, margarine) in the “good” category.

See alsoThe Best & Worst Cooking Oils for Healthy Fat. 

That turned out to be not only simplistic, but also wrong.

Vegetable oils are loaded with omega-6, which, for all intents and purposes, are pro-inflammatory. In contrast, omega-3 fats are anti-inflammatory. You actually need both, but they need to be in a balanced ratio, somewhere between 1:1 and 4:1. Largely due to the myth that vegetable oils are always good, we’re currently consuming a staggering 16 times more omega-6 than omega-3. No wonder inflammation – a promoter of every degenerative disease we know of, including obesity – is so prevalent.

One Achilles’ heel of high-fat diets is that they’ve been low in fiber. After all, fat has no fiber at all, protein has only trace amounts, and high-fiber foods like beans have too many carbs for those trying for nutritional ketosis. 

On the Smart Fat plan, you’re encouraged to eat high-fiber foods, specifically legumes, low-sugar fruits like grapefruit and berries and some low-glycemic carbs like quinoa and oatmeal. As far as we know, Smart Fat is the first time high-fiber and high-fat have been combined in one plan.

A high-fat, high-fiber, high-flavor, moderate-protein eating plan is looking to be a winner for weight loss. Emerging research suggests it may also be good for a whole lot more.

Want to slim down for summer? Join our dietitians, Erin Macdonald and Tiffani Bachus, for their new Clean Eating Academy course, A Whole-Life Guide to Lasting Weight Loss. Class begins April 27. Register now.