What is the Keto Diet? The Science Behind a Completely Different Way to Fuel your Body.

I’m sure you know that your body runs on glucose… but what if I told you there is an alternative, more efficient, energy source?

No matter what kind of food you eat, the outcome is the same – burning food for energy. It’s a complex process, but the simple message is that by changing to a keto diet, you can change the way your cells power themselves.

Not only will you burn fat, but ketosis will also power your brain,heart and body more efficiently!

So what is the keto diet, and how can it benefit you? Read on and find out!

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Normally, your cells are powered by an energy molecule called ATP, made by using glucose. Ketosis is different – put simply, it creates molecules called ketone bodies, by using fats. It is a part of the normal bodily process, and it takes place regardless of how many carbs you eat.

Ketone bodies, however, are a much more effective way of powering your body. It does require more energy to get going, which is why your body prefers the easier-to-use glucose, but ketosis provides far more energy in return.

“We evolved to produce ketone bodies so we could not only tolerate but also thrive in the absence of glucose for prolonged periods of time. No ability to produce ketone bodies = no human species.”

-Dr Peter Attia, MD, The Eating Academy

Your Diet, Digested

Before we get into the differences between powering your body with glucose vs. ketones, let’s dive into the different ways your body converts food into energy.


Carbs are composed of chains of simple sugars. Complex carbs are longer chains of sugars, and they simply take more energy to digest. Enzymes break carbohydrates down into glucose, the simplest sugar and main form in which energy is normally carried in your blood stream.

-Glucose is an easy energy source – but isn’t steady or efficient. Consuming excess is the easiest way to create body fat.

Dietary fats are made from chains of fatty acids attached to a glycerol molecule. These are triglycerides – the stable, storage form of fat. The best kind to eat are saturated and monounsaturated, and high in Omega-3. These are found in animal sources, nuts, coconut, and avocados.

-Fats are the most energy dense food we consume. One gram of fatty acids yields about 9 kcal (37 kJ) of energy, compared to only 4 kcal (17 kJ) for carbohydrates and proteins.

-During digestion, enzymes break down fats into glycerol and fatty acid chains. Fatty acids can then enter the bloodstream and be absorbed into cells, where they become fuel. The glycerol is either recycled to become glucose or it binds to fatty acids again to become body fat.


Proteins are made from long, folded up chains of amino acids. They are digested into smaller chains, or peptides, in your gut and then absorbed. Once in your cells, peptides are broken down into their amino acids.

– Proteinogenic amino acids, which are used to make new cells in your brain, muscles and other tissues.

– Nonproteinogenic amino acids, which are used for energy. These are the amino acids we’re most interested in. About half of these are converted into glucose, so eating too much protein can inhibit your body from carrying out ketosis. The remainder can be used to make ketone bodies.

Body Fuel 101

As you probably know, the main way your body stores excess energy is in fat. The average adult has anywhere from 15-40lb of body fat, but also stores condensed carbohydrate energy in the form of glycogen – around 0.7lb in the liver, and minor amounts in muscles and other tissues.

Glycogen is easily converted into blood glucose and helps prevent spikes in blood sugar levels between meals or after intense exercise. Usually, your body constantly replenishes glycogen, but during fasting, your glycogen storage becomes drained within a few days.

Cells take in glucose and use enzymes to change it into fuel. When your blood glucose increases to levels above what your body immediately needs, insulin is released. This phenomenon triggers the formation of glycogen, and eventually, energy storage as fat.

Ketosis is different.

What is a keto diet based on:
  • a high level of fats
  • a medium level of proteins
  • and a very low amount of carbs

Your body doesn’t really need carbs because your liver will always make sure you have enough glucose to perform at an adequate level and maintain the health of your body. By decreasing your carbohydrate intake dramatically, you are taking the first step towards ketosis.

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When you radically decrease your body’s supply of accessible glucose, your body’s next option is to break down your glycogen stores.

This process is instigated by the release of the hormone glucagon, which has basically the opposite effect of insulin. Once this source is also exhausted, your body turns to your fat stores and muscles.

If you’re maintaining your muscle mass with exercise and dietary protein, your body will take energy from your fat stores first. Otherwise, it can start converting muscle protein back into amino acids, which will then be used as fuel.

You will lose weight, but muscle is not the kind of weight you want to lose! By taking care of your muscles, fat becomes an easier source of fuel, breaking triglycerides down into glycerol and fatty acids. This is why ketosis is known as the fat-burning state!

[Tweet “Discover why ketosis is known as the fat-burning state.”]

The other important part of answering the question “What is a keto diet?” is know that it is not a ‘diet’ – a study by Rockefeller University observed,

“in individuals who moderately reduced their daily caloric intake, 91% of the loss was fat and only 9% was muscle. But in subjects who severely reduced their daily caloric intake, fat represented 48% of the total weight loss and muscle 42%. In other words, the greater the daily calorie restriction, the greater the loss of muscle mass.”

You need to maintain your fuel intake – energy dense, low-carb, fats and proteins. When you combine this with exercise, your body will start using these non-glucose sources and enter ketosis.

Manipulate Your Metabolism

Okay, so here’s how this works.

One of the main metabolic processes of human cells is the Krebs Cycle, a series of enzyme reactions that result in the creation of energy for the cell. Glucose goes in, energy comes out. The process is named for Dr Hans Adolf Krebs, who received a Nobel Prize for its identification in 1937.

“This poses a real evolutionary dilemma. We need an enormous amount of energy just to not die, but the single most important organ in our body [the brain] (also quite energy hungry in its own right) can’t access the most abundant source of energy in our body (i.e., fat) and is, instead, almost solely dependent on the one macronutrient we can’t store beyond a trivial amount (i.e., glucose).”

-Dr Peter Attia, MD

So, what happens when you have no more available glucose or glycogen?


Adventuring into Ketosis

Instead of the Krebs Cycle producing the simple fuel molecule ATP, ketone bodies are formed in liver cells.

Our bodies are said to enter ketosis at the point when blood sugar and liver glycogen are no longer present, and our system resorts to using ketones for fuel. At this point, not only is our body doing the natural thing, and burning off fat, it’s also powering up our brain! We can jump start ourselves into ketosis with a brief fast, allowing our body to quickly burn through the carbs that are in our system, and turn to fat for fuel.”

Dr David Perlmutter, MD, neurologist and author

Without a supply of glucose, cells use fatty acids as a fuel source instead.

Remember how fatty acids are way more energy-rich than glucose? As a result of relying on these fatty acids, excessive amounts of energy are produced – way too much for the cell to use, but this form of fuel can’t exit the cell.

In order to actually use this energy source elsewhere, the Krebs Cycle combines the fatty acids with those nonproteinergic amino acids to create ketone bodies. These are able to circulate in the blood.

This process makes 46% more fuel for your body!


This isn’t to say that your body can run on ketones alone.

“The idea that your body doesn’t need glucose at all is silly. Your body definitely needs it. However, your body doesn’t need as much of it once it has gotten used to ketones for fuel. The large spikes of sugar (which spikes insulin) is what is dangerous. So what we need to stay healthy is a low and constant supply of glucose.”

-Derek Tran, author of Asian Without Rice

Acetoacetate, the first and most basic ketone, makes an excellent fuel. But acetoacetate also makes another ketone – acetone. Acetone is also an energy source, but around 30% is expelled in your breath and urine, unfortunately causing ketosis’ iconic fruity breath.

One important organ that can’t use fatty acids directly as a fuel source is your brain. Fatty acids can’t cross the blood-brain barrier, the filter that protects your brain from certain substances. What the brain can use, however, are ketone bodies.

After becoming keto-adapted (ketone powered) for a while, your muscles start converting the acetoacetate into a more complex ketone body, beta-hydroxybutyrate (BHB). This travels easily into the brain.

Your brain prefers BHB for fuel, and it runs up to 70% more effectively than it does when using glucose. More brain power!

Weighing the Benefits

Brain power! Energy! Smelly breath! Oh.

Over time, the bad breath will improve, I promise. Your body will expel less ketones, and you’ll lose body fat. You are not experiencing starvation, nor is ketosis slowing down. Your brain is burning BHB for fuel, and your body is trying to give it as much efficient energy as possible.

Some people find the first few days of a keto diet a little bit rough. In the few days between reducing carbohydrates and the time when your body starts entering ketosis, you may feel light-headed, lethargic or dizzy. Your body hasn’t started burning fat for fuel yet… but it will. And when it does, you’ll feel the benefits.

As a bonus, studies show that ketones have an effect on levels of ghrelin (the hunger hormone) and cholecystokinin (CCK – the satiation hormone).

How hungry you are before you eat and how much food you want to consume are both important factors in maintaining a healthy body.

When your body is in ketosis, CCK levels are elevated, causing you to feel full sooner, and you will also be able to go longer without feeling hungry. Ketosis prevents levels of ghrelin from getting too high – meaning less hunger pangs and cravings.

Steps for success

These are the basic tenets of a keto diet:

  1. Keep exercising. This prevents muscle loss as your metabolism changes.
  2. Reduce your carbohydrates to about 50g/day
  3. Increase your healthy fats, such as coconut and avocado. Have you tried grass-fed butter in your coffee??
  4. Eat a moderate amount of protein (about the size of your palm).

Your brain runs far better on ketones, your body fat is being used for fuel, you’re building muscle and you’re not getting hangry. It’s time to change your perception and kick carbs from the base of the food pyramid.

It’s science – hack your metabolism and feel amazing!

For more info on eating a ketogenic diet:
Ruled.me – The Keto Diet In A Nutshell
Is Ketosis Dangerous?

Images: cmgirl/ Shutterstock, stickerama/ ShutterstockSudowoodo/ Shutterstock

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