Back in the 1950s, a scientist named Ancel Keys began claiming that saturated fat caused heart disease. His research looked pretty convincing at the time, and his theory launched the beginning of a powerful fat-fearing era in nutrition.

Unfortunately for generations of nonfat milk-drinking, chicken breast-eating Americans, Keys’ research is not only flawed, but there’s evidence that he manipulated his data to make sure that fat looked bad (bringing himself fame and grant money in the process). Even worse, there’s also evidence that sugar industry bigwigs have been paying scientists to shift the blame for obesity and chronic disease from sugar to fat since the 1960s.

It turns out that science doesn’t support low-fat claims at all.

But it was too late. Food manufacturing companies began pumping out low- and nonfat products, and pouring in the sugar to compensate for their bland food. Soon, grocery store shelves were filled with sugary, processed “diet” foods and people were getting fatter than ever.

After 60 years of low-fat propaganda, the “fat makes you fat” rhetoric is so ingrained in our collective psyche that many people still fear fat, even though study after study shows that fat is harmless. In fact, eating more fat is the single most powerful way to hack your cravings, turn on your brain, manage weight, and balance your hormones. Fat isn’t just good for you; it’s essential.

Adding more fat to my diet was a leap for me at first, too. It went against everything I’d ever been told about healthy eating. But the more I looked into the research, the more it became clear that fat (especially saturated fat) and cholesterol are actually the building blocks for a thriving body and mind.


When I began researching the Bulletproof Diet, I wanted to see just how quickly eating more calories from fat could make me gain fat. So, I stopped exercising, cut my sleep to less than 5 hours a night, and started consuming between 4,000 and 4,500 calories from the Bulletproof Diet per day, with about 70% of my calories from quality fats (more on fat quality later).

I started to see a difference almost immediately. My focus increased, I ran on less sleep, I started losing weight, and my inflammation began to disappear. I even grew abs.

If you’ve ever tried traditional dieting, you know that low-fat, low-calorie diets leave you miserable. They’re unsustainable. You’re hungry all the time and the weight you lose comes right back after you stop dieting.

Quality fats, however, are clean-burning energy sources that keep your body and brain running at maximum capacity. It’s time to end the era of fearing fat. Let’s look at some of the ways fat actually helps you.


  1. Dietary fat contains more energy per gram than any other nutrient, so it’s the most effective way to deliver energy to the parts of your body that need it, like your brain.
  2. Compared with protein or carbohydrates, fat has the lowest impact on insulin levels. Insulin spikes are what lead to energy crashes and weight gain. Insulin is the body’s response to high blood sugar. You don’t want your pancreas constantly pumping out insulin because it will get tired and give up on you. That’s when diabetes happens.
  3. Fat slows the absorption of carbohydrates, keeping blood glucose levels under control. When blood sugar is high, so is cortisol, your body’s main stress hormone. Circulating cortisol will keep blood sugar high and can contribute to inflammation and hurt your immune system.
  4. Fat makes you feel fuller longer. You will actually eat less if you trade empty processed grains and sugar for quality fats.
  5. Quality fats often contain fat-soluble vitamins like vitamins A, D, E, and K. Eating fat alongside other nutrient-dense foods will increase the fat-soluble nutrients you absorb from them, too. That’s why it’s a good idea to eat fat at every meal, and especially with your vegetables. Good thing butter and veggies pair so well together.
  6. Fat is a building block. Quality fats form strong cell membranes and help build sex hormones. Your brain is the most fat- and cholesterol-dense part of your body and it requires saturated fat to build myelin, the insulators that connect many of your brain cells to one another. Low-fat diets will starve your brain. Because the healthy fats in the Bulletproof Diet help to maintain and balance hormones, you will be able to manage your weight more effectively.
  7. Caloric restriction is not the answer. Sure, you can starve yourself thin. But different foods go through different metabolic pathways in the body, which is why bread can make you fat and butter can thin you out. Long-term caloric restriction can stress your body and contribute to leptin resistance, insulin resistance, low testosterone, and thyroid issues, which is why so many people lose weight in the short-term, then gain it all back when they begin to eat normally again. Plus, on fewer calories, you’ll feel hungry all the time, so you’ll be more likely to “cave” and eat an entire pizza. Satiate your body and brain with good fats and your cravings disappear.


There is no evidence that saturated fat is bad for your heart. In fact, one of the most famous studies on fat and coronary health showed that yes, a diet lower in saturated fat will lower your cholesterol, BUT lowered cholesterol does not ensure a long life! There was actually an increase in mortality in participants following a “heart healthy” diet of mostly linoleic acids from corn oil, as opposed to delicious fats from foods like grass-fed beef and butter.

Of course, this is only one study. There are plenty more systematic reviews looking at the link between saturated fat and heart disease, and no one can prove that saturated fat from quality sources cause heart disease.

In fact, there are several studies that suggest saturated fat can reduce the risk of stroke.


  1. Learn your fats. Not all fats are created equal. Some fats feed your brain and help turn off your cravings, while some cause inflammation and make you crave terrible foods. Get all the benefits of a high-healthy-fat diet by adding more of the good fats to every meal. Start with grass-fed butter or ghee and Brain Octane Oil. You can read more about different fats here.
  2. Focus on quality, not quantity. Calories-in, calories-out is a myth. If it were true, then I would have gained dozens of pounds of fat when experimenting with a high-fat diet at 4,500 calories per day and no exercise. When you focus on the quality of your food and the nutrition it provides, cravings subside, and your body will start to regulate your caloric intake naturally. This results in the fat loss and mental clarity that so many people experience on the Bulletproof Diet.
  3. Try it. Everyone’s different. If I’m wrong and your body doesn’t thrive on healthy fats, eliminating processed grains, and limited starchy carbs, you’ll be able to tell. If you gain weight or feel like crap, or if your blood results start to let you know you’re going in the wrong direction, stop what you’re doing and reassess.
  4. Bulletproof your fatty experiment. If you’re upping fat, you’ll want to limit your carbs. You’ll probably gain weight if you mix the two together. Start here with the main tenets of the Bulletproof Diet to set yourself up for success. And check out this post to avoid the top three mistakes many people make when going Bulletproof.


Brain Octane Oil. A reliable and quick source of energy for your brain and body. Brain Octane is made up of the most powerful MCT, distilled from 100% pure coconut oil to support cognitive performance and fat loss.[9]

Grass-fed butter and ghee contain some fat-soluble vitamins and essential minerals, as well as a short-chain fatty acid called butyrate, which is essential for gut health and brain function.

MCT Oil. A slightly less potent form of Brain Octane Oil, MCT oil will still give you a quick source of energy from fat, not sugar.

Coconut Oil. The fat-burning component of coconut oil is found primarily in its medium-chain-triglyceride, or MCT, content. MCTs reduce your appetite naturally and increase the rate at which you burn fat—at rest! [10,11,12, 13] The most powerful MCT is called C8, and it’s up to four times stronger than regular coconut oil. That’s what makes up Brain Octane Oil, the cleanest burning energy source out there!

Dark Chocolate contains theobromine, a gentle stimulant that’s related to caffeine but more mellow. Theobromine also increases blood flow and may explain, at least in part, why chocolate is an aphrodisiac. Dark chocolate is also full of fiber, copper, manganese, antioxidants, and tasty fat. Go for 70% dark or darker, and be mindful of added sugar.

Pastured Egg Yolks. Pastured eggs are packed with protein, B vitamins, zinc, and other nutrients that help balance hormones and support muscle building. Egg yolk also contains easily absorbed lutein and zeaxanthin, carotenoids that contribute to eye health!

Krill Oil and Fish Oil. Omega-3 fatty acids provide a launchpad for making hormones that regulate blood, heart, and metabolic function.

Grass-fed red meat and marrow. High-quality grass-fed meat contains essential nutrients, from the protein that acts as the building blocks of muscles and other tissues, to zinc, iron, and even pretty decent levels of brain-boosting omega-3 fatty acids. Here’s a closer look at grass-fed beef and the benefits of adding some grass-fed red meat to your diet.

Extra Virgin Olive Oil. EVOO is very high in antioxidants and anti-inflammatory oleic acid. It’s better not to heat EVOO. Doing so will destroy many of the precious nutrients and denature the delicate fats. Instead, drizzle it over your meal right before you eat it. Always buy olive oil bottled in dark glass, too. Clear bottles let light through, which oxidizes (destroys) nutrients the longer the bottle sits on a shelf.

Avocado Oil looks a lot like olive oil in terms of nutrition. It’s a lot more heat-stable than olive oil, so you can cook with it or add it to your meal in sauces and dressings.