If you believe the buzz, ketosis — whether via the almost-zero-carb ketogenic diet or via ketone supplements— can curb appetite, enhance performance, and cure nearly any health problem that ails you. Sound too good to be true? It probably is.

++++

Wouldn’t it be awesome if butter and bacon were “health foods”?

Maybe with a side of guacamole and some shredded cheese on top?

“I’m doing this for my health,” you could purr virtuously, as you topped your delectably marbled, medium-rare steak with a fried egg.

Well, many advocates of the ketogenic diet argue exactly that: By eating a lot of fat and close to zero carbohydrates you too can enjoy enhanced health, quality of life, performance, brain function, and abs you can grate that cheese on.

So, in this article, we’ll explore:

• What are ketones, and what is ketosis?
• What, exactly, is a ketogenic diet?
• What evidence and scientific research supports the ketogenic diet?
• Do ketone supplements work?
• Is the ketogenic diet or ketone supplementation right for me?

How to read this article

If you’re just curious about ketogenic diets:

• Feel free to skim and learn whatever you like.

If you want to change your body and/or health:

• You don’t need to know every detail. Just get the general idea.
• Check out our advice at the end.

If you’re an athlete interested in performance:

• Pay special attention to the section on athletic performance.
• Check out our advice for athletes at the end.

If you’re a fitness pro, or interested in geeking out with nutritional science:

• We’ve given you some “extra credit” material in sidebars throughout.
• Check out our advice for fitness pros at the end.

It all started with the brain.

If you’ve called Client Care at Precision Nutrition, you might have spoken to Lindsay.

Aside from being an incredibly helpful and friendly voice on the other end of the phone, Lindsay is also a tireless advocate for a health condition that has shaped her life in many ways: epilepsy.

Epilepsy is an ancient brain phenomenon, known to medicine thousands of years ago. To manage it, our Neolithic ancestors drilled holes in one another’s skulls, perhaps trying to let the bad stuff out — a practice known as trepanation.

Around 400 BCE, the ancient Greek doctor Hippocrates observed a man who had seizures for five days. On the sixth day, he noted, as the patient “abstained from everything, both gruel and drink, there were no further seizures.”

About 1,400 years later, in 1000 CE, the famous Persian physician Avicenna — who coined the term “epilepsy”, from the ancient Greek verb epilambanein (to seize or attack, as the neurological condition caused seizures), speculated that “overfeeding” might be a risk factor for epilepsy.

By 1911, a pair of Parisian doctors were trying fasting as a treatment for children with epilepsy, and in the United States, physical culturist Bernarr McFadden was claiming that fasting for three days to three weeks could cure anything.

Despite not having the tools and insight of modern neuroscience, these and other people who explored fasting and dietary prescriptions for neurological disorders were on to something.

We now know that there may be a dietary connection — not just between epilepsy and what we eat (or don’t), but also with many other brain disorders.

Unfortunately, fasting isn’t fun. We evolved with a pretty strong aversion to starvation, and our brains and GI tracts have lots of ways to make sure we eat enough.

Which raises the question:

Could we get the health benefits of fasting another way?

In other words:

Could there be “fasting without fasting”?

In 1921, two things happened.

One: Endocrinology researcher Rollin Woodyatt noted that the same chemical environment happened with both starvation and a diet that was very low in carbohydrates and very high in fat.

Two: Dr. Russell Wilder wondered:

Could a person get the health benefits of fasting without actually fasting?

He and other doctors at the Mayo Clinic experimented with what Wilder called the “ketogenic diet” during the early 1920s. Not only did children with epilepsy seem to improve overall with this type of diet, they seemed to think and behave better as well.

Proven by several notable medical authorities, a ketogenic diet as a treatment for childhood epilepsy found its way into medical textbooks by around 1940, and stayed there throughout the 20th century.

In 2016, aging, contact sports, and modern warfare now present us with new populations of people whose brains might benefit from a ketogenic diet:

• people with neurodegenerative disorders (such as multiple sclerosis, Parkinson’s, and Alzheimer’s); and

• people with traumatic brain injury (TBI) from events such as explosions or concussions.

First the brain, then the body.

There was another group of people who became curious about ketogenic diets some time in the 1980s and 1990s: bodybuilders and physique athletes.

These folks weren’t too concerned about brain health or longevity. They wanted to be ripped.

The ketogenic diet seemed like a magic bullet: a way to eat butter, bacon and cream, and still get abs.

Today, what’s old is new again.

Physique- and performance-conscious people, as well as people looking to maximize lifespan and life quality, have rediscovered this old-school dietary paradigm and are wondering:

• Could a ketogenic diet help me perform better?
• Could a ketogenic diet help me live longer?
• Could a ketogenic diet help me look great on the beach?

The answer?

It depends. (Don’t you hate that? But it’s true.)

To understand why, we’ll look at:

• the science of ketosis;
• what a ketogenic diet looks like in “real life”;
• who it might work for (and might not work for); and
• what this means for you.

Let’s start by clarifying just what a ketogenic diet is.

What does a ketogenic diet look like?

It might be hard to translate “low carb, high fat” into everyday foods.

To give you a better idea of the ketogenic diet in real life, here’s a comparison:

	Protein	Carb	Fat
PN Mixed Meal	~30%	~40%	~30%
Paleo Meal	~40%	~20%	~40%
Low-Carb Meal	~40%	~10%	~50%
Ketogenic Meal	~20%	~5%	~75%

And here’s what that might look like translated into meals.

Notice a few things.

Protein

For the first three meals, protein is more or less the same, with a little variation.

Ketogenic diets, on the other hand, include less protein — usually closer to 10 or 20 percent of total daily intake.

Extremely low in carbohydrates

The Precision Nutrition plate suggests high-fiber, slow-digesting carbohydrates, such as whole grains, beans and legumes, fruits, and starchy vegetables.

The Paleo plate may contain slightly fewer carbohydrates (early human diets often had plenty of them), but eliminates the grains and beans / legumes.

The “low carb” plate will have fewer carbohydrates than the first two, but still have a small amount, likely from vegetables.

The ketogenic meal shoots for near-zero carbs. Most estimates suggest around 10-15 grams of carbs a day. To give you an idea of what this looks like, that’s about one fist-sized portion of cooked carrots, or about 10-15 grapes. For the whole day.

Very high in fat

The Precision Nutrition plate suggests about 1-2 thumb-sized portions of fat-dense foods (like nuts, cheese, avocado, olive oil, etc.) per meal, depending on body size, activity level, and goals.

The Paleo and low-carb plates may be roughly similar, with a little variation.

We might call all three of these “moderate fat”. Indeed, some indigenous diets (aka variations on the “Paleo” concept) are often quite low in fat, especially saturated fat.

The ketogenic meal, on the other hand, is high fat — even up to 90 percent of total energy intake. That means if you’re eating a 500-calorie spinach and mushroom salad, you get about 2 thumb-sized pieces of chicken breast on top, and then pour about 3-4 glugs of olive oil on top… Yum yum!

Highly restrictive

A ketogenic diet is the most restrictive and limited of all four of these styles of eating. Here’s what you can eat on a ketogenic diet:

A small amount of protein, such as:

• meat
• poultry
• fish
• seafood
• eggs

A large amount of high-fat foods, such as:

• avocado
• coconut and coconut milk or oil
• olive oil and any other oil
• nuts and nut butters
• bacon
• egg yolks
• butter
• cheese

A very small amount of very-low-carbohydrate vegetables, such as:

• leafy greens
• brassicas: broccoli, cauliflower, Brussels sprouts, cabbage
• asparagus
• cucumber
• celery
• tomatoes
• peppers
• mushrooms
• zucchini

Here’s what you can’t eat on a ketogenic diet:

• Most dairy (except high-fat items like butter and certain cheeses)
• Fruit
• Grains
• Beans and legumes
• Starchy vegetables (such as sweet potatoes)
• Slightly-sweet vegetables such as winter squash, beets, or carrots
• Most processed foods (with the notable exception of pork rinds)

So, let’s recap:

Ketogenic menus:

• Vary in the proportion of protein but are generally low.
• Stay as close to no-carb as possible.
• Are very high in fat.
• Are very limited in food choices.

So why go to all this effort?

Well, for particular groups of people, ketosis may indeed be helpful.

(For other people, of course, it may not be helpful… and it may be actively harmful. We’ll talk more about that in a moment.)
•••••••••
To understand why this is true, let’s look at how ketosis actually works.

What is ketosis?

The role of ketones

Ketones are a group of organic compounds with a specific structure.

The term “ketone” was actually coined around 1850 by German chemist Leopold Gmelin, along with the term “ester”. (See? Not as new as you’d think!)

We can use two types of ketones as energy sources, acetoacetate and D-β-hydroxybutyrate. (The β sign means “beta”.)

Our body can make ketones through a complex biochemical pathway.

The pathway to ketosis

Put very simply, when the conditions are right (for instance, during starvation or fasting, or when our carb intake is very low):

• Our body releases fatty acids from our stored body fat.

• These fatty acids enter other cells.

• Fatty acids are combined with co-enzyme A to form acetyl-CoA chains.

• These chains move into the mitochondria (our cells’ energy factories).

• The chains are broken down into acetyl-CoA units by a sequence of reactions known as β-oxidation.

• Chemical magic happens.

• Acetyl-CoA forms your friends the ketones: acetoacetate and β-hydroxybutyrate, along with acetone (the same smelly stuff in your nail polish remover).

• Ketones are released by the liver into the blood.

• Almost any cell that needs energy can grab it from these circulating ketones. Again, our brain will be the greediest for these nummy little molecules.