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Becoming Fat-Adapted

fat adapted

Becoming fat-adapted is the goal of keto. You want your body to become incredibly good at burning fat. Once you are a fat burner, you will begin to see the excess weight melt away! Fat burning is possible once your body has become fat-adapted. In other words, your body prefers fat over sugar as its primary fuel source. This is also considered the state of ketosis. So, how do you get to this place of burning fat and the weight loss that you so desire? Well, in the previous article I explained the basics of keto including the proper macros and some of the benefits of keto. Today I am going to show you exactly how to become fat adapted.

Sugar Stealing the Show

Whether you think you eat a lot of sugar or not, your body is fueled by sugar. This is simply the result of a carb-loaded diet. When you feast on carbohydrates continually, you are feeding your body sugar. While there is likely more nutritional value, depending on the carb, than a Snickers bar, these carbs are still sugar in the body. Let me explain what I mean.

The Makeup of Carbs

Carbohydrates fall into one of two categories: simple or complex carbs. A simple carbohydrate is made up of one or two unit structures. For instance sucrose is a two-sugar molecule made up of glucose and fructose. A complex carbohydrate is composed of polymers (I.e. repeating chains) of glucose. Nearly all carbohydrates are converted into glucose as they are moved into the bloodstream. The exception is fructose. The body is not able to convert fructose into glucose, so it is instead made into fat by the liver.

Once glucose is in the bloodstream, it needs to be moved in order to keep blood sugar within a normal range. Where does all of this glucose go? The muscles either burn glucose immediately or store excess as glycogen in the cells for later use. The liver also stores glucose as glycogen and releases it during sleep and exercise to help maintain normal blood sugar levels. Some of the glucose is used by the brain. Much of the glucose that enters the body, especially in a high-carbohydrate diet, is stored as glycogen. When the glycogen stores are full, the liver and cells turn the excess glucose into fat – a process called lipogenesis. One important note on this process is that the body is not able to turn this fat back into blood sugar. Hence, the excess fat that you so desperately want to rid your body of!

Carbohydrates are Necessary, Right?

Of course it would be obvious to believe that carbohydrates are necessary for our bodies. After all, we labeled them a macronutrient. Critics of keto regularly cite this when arguing against keto, stating that carbohydrates are necessary for our bodies. They cite that it can’t be healthy to avoid an entire macronutrient. So, are carbohydrates necessary?

The primary indication for the need of carbohydrates is that of maintaining blood glucose levels. Again, critics claim that carbohydrates are necessary for maintaining proper levels of blood glucose. However, as Jeff Volek and Stephen Phinney write, gluconeogenesis and adaptation combine to “allow us to maintain blood glucose levels without dietary carbohydrate.” 1 This is not an argument against dietary carbohydrates, but rather an argument against the claims that carbohydrates are necessary for our body to maintain adequate blood glucose levels.

The Role of Insulin

Insulin plays an important role in the body’s ability to process carbohydrates and regulate blood sugar. In fact, insulin is the primary player in this process. Insulin is a hormone released by the pancreas in response to glucose in the bloodstream. The role of insulin is to regulate blood sugar by shuttling the glucose into the cells for immediate use or into glycogen stores (this includes fat stores). Excessive carbohydrate consumption increases stress on the pancreas and elevates insulin production in order to constantly maintain blood sugar levels. Fat, on the other hand, greatly reduces the need for insulin which lead to less insulin dependence. Continued adherence to a high-carb diet commonly leads to insulin resistance, or diabetes in extreme cases.

Insulin Resistance and Diabetes

Isulin resistance occurs when insulin production is high to account for the excessive carbohydrate consumption, and therefore high levels of glucose in the bloodstream. Over the time, the body develops a resistance to the work of insulin causing the liver to over-produce insulin. The result is that the liver turns more of this excess glucose into fat leading to weight gain, especially around the mid-section. Insulin resistance is often referred to as “metabolic syndrome” and is typically a precursor to diabetes.

Diabetes is when the body is unable to dispose of glucose in the bloodstream and is classified by two types: Type 1 and Type 2. Type 1 Diabetes, the more severe of the two, is when the liver is unable to make insulin. Type 2, similar to insulin resistance, is when the liver is able to make insulin but the cells ignore the insulin.

Excessive carbohydrate consumption runs a muck in the human body. Yet, carbohydrates are the darling of most, if not all, dietary and nutrition plans (including the USDA). What is worse is the quality of these recommended carbohydrates, but more on that later. For now, I want you to see that excessive carbohydrate consumption is making you fat. Insulin is quickly moving all of the excess glucose into fat and that fat cannot be turned back into blood sugar. So, how are you going to change this process? You must become fat-adapted!

The Power of Fat

With carbohydrates, the primary fuel source your body uses is glucose. The muscles, liver, and even brain depend on glucose as a source of fuel. While your body does need glucose, it doesn’t need as much as you think. The goal of keto is to switch the fuel source of the body from glucose to fat. There is far more energy to be had in fat as a fuel source!

Fat as Fuel

How do you switch the body from burning glucose as fuel to fat as fuel? The simple answer is to reduce carbohydrates and increase dietary fat. Before you go throwing out all of your carbs and start loading up on bacon and butter, let me help you understand how this works.

The first and foremost aspect to this idea of fat as fuel involves the reduction of carbohydrates. When carbs are restricted, insulin production is greatly reduced. Remember fat doesn’t trigger insulin. Already, by reducing this insulin response in the body we are limiting the glucose movement in the body. The body is getting just enough glucose for the muscles and glycogen stores without the excess that is stored as body fat.

Fat, because it doesn’t dissolve in water, is carried by the bloodstream to deliver fuel to the cells. These fats are carried as lipoproteins and carry cholesterol along with them. Oh no, we used that dirty term cholesterol. However, cholesterol is necessary for the movement of fat and fat soluble nutrients to the cells.

Both fat and glucose are necessary for the cells in your body. Some cells prefer fat, while others prefer glucose, and some prefer specific amino acids. So what do each of these cells prefer?

The muscles prefer fat when at rest and only use glucose when insulin levels are high. Even during exercise, the muscles prefer fat when the intensity levels are around 50-60%. When intensity levels are above 60%, glucose is preferred. The heart, when the body is not exercising, also prefers fat for fuel and rarely uses glucose.

The liver, with all of its many functions in the body, is another organ that prefers to get the majority of energy from fat. The liver is able to get fat from circulating fatty acids, remnant lipoproteins it removes from circulation, and it can even make fat from carbs.

The brain is perhaps most surprising of all. The brain does not burn fat, but rather burns both glucose and ketones (more in the next section). The brain doesn’t contain a reserve supply of glycogen, and since it cannot burn fat, is completely dependent on the constant blood supply of fuel and oxygen. This would be an example of why you notice a physiological response when your blood sugar dips too low.

Now, before you advocate that one of the most important organs in the body requires glucose, let’s take a look at ketones. Remember, the brain is capable of running on both glucose and ketones!

Production of Ketones

Ketones are produced in the liver and are a result of fat adaptation. When the body is starved of glucose and has depleted its glycogen stores, typically a result of reduced carbohydrates, it turns to another energy source. This source is fat. As the body begins to break down these fatty acids to use for fuel, a process known as beta-oxidation, ketones are formed for use as a fuel for the brain and body. This state of ketone production is what is known as ketosis. Ketones are a much better energy source than glucose. In fact, ketones are able to produce more energy than glucose. Not only do they produce more energy, but the source of energy is far more stable and sustainable. The brain also functions much better when burning ketones as opposed to burning glucose.

Burning Body Fat

Carbohydrate restriction causes the body to burn fat and produce ketones. This leads to far greater energy and brain function among the numerous other benefits. One of those benefits is weight loss! You will notice significant weight loss with carbohydrate restriction, namely keto, as your body burns fat. This works because once the body runs out of dietary fat to burn for fuel it will look to other sources. The body will now look to stored body fat to burn for energy. When your body is truly fat-adapted, it will run on fat as its primary energy source. This is when you are able to experience true and significant weight loss. The beauty of this kind of weight loss is that your body is actually burning its own stored body fat as opposed to continually burning through glycogen stores as in other diets. As you can already tell, keto isn’t about calorie restriction and intense exercise. It is about cutting down on the harmful carbohydrates and letting your body run on its natural fuel source: fat!

Keto is about far more than just getting rid of carbs, increasing fat, or losing weight. It is about turning your body from diabetes causing carbs and toward what is natural for the body—burning fat. This is the way the body was designed. Fat burning is natural, but it can only begin when the carbs are dramatically restricted. Once this happens, you are well on your way to becoming fat-adapted!

Are you willing to restrict carbs in order to become fat-adapted?

  1. Volek, Jef PhD, RD & Phinney, Stephen MD, PhD. The Art and Science of Low Carbohydrate Living, 48.