Ketosis, also known as “nutritional ketosis”, has to do with your body’s fuel usage. Under regular circumstances, it relies on three energy sources:

1. Glucose (carbohydrates)
2. Free fatty acids (fat)
3. Amino acids (proteins)

Which of those your body primarily uses depends on various factors, among them hormonal status, liver glycogen storage, enzyme concentrations, and activity levels. The most important factor, however, is your macronutrient intake ratio. We will discuss in more detail later, what macronutrients are.

If you consume lots of carbs, as most people do, your body will use mostly glucose for fuel, which believe it or not is not the most effective fuel for your body.  However, if you limit your carb intake as much as possible and consume fats instead (i.e., a low carb and keto diet), your body will burn more free fatty acids and fewer carbs. In other words, your body will turn into a fat-burning machine.

Now, if you consume almost no carbs, your body will not have much glucose to use for fuel. Instead, it will run on fatty acids. The thing is, some of your tissues, your brain being a prime example, cannot use fat for fuel. 

The problem is that your body can only store about 500 grams of glycogen at any one time – an amount that can be depleted within one or two days. Of this, around 400 grams are stored in your muscles and about 100 grams in your liver. Thus, if you restrict your carb intake for longer than this period, your brain would soon be without fuel.

Fortunately, mother nature has provided a solution to this problem: ketones. Ketones are chemicals produced in your liver when your body breaks down fat for fuel during low glycogen levels. Various tissues, including your brain, can use these ketones for fuel when glucose is absent. That is an excellent outcome because you would die otherwise. 

When your body uses predominantly fatty acids and ketones for fuel, you are in a state of “nutritional ketosis.” 

To get into ketosis, your system must produce ketone bodies. You achieve this by restricting your carb intake below a certain threshold. Many “gurus” say this carb threshold is the same for everyone. For instance, if you eat less than 50g of carbs a day, you will achieve nutritional ketosis, according to them. But that is not true! Various factors affect the ability of your body to get into ketosis. These include age, body weight, body fat percentage, hormonal health, and medical conditions.

That said, keeping your net carb intake below 50g a day causes most people to get into nutritional ketosis. That is why I encourage my clients to observe this limit. To make sure you are indeed in ketosis, you should track your state of ketosis.

This is an important distinction to understand.  

Due to the phonetic similarity, many people confuse ketosis and ketoacidosis. This is even the case with medical doctors. That is why the keto diet often gets a bad rep. So, let me be crystal clear here, ketosis and ketoacidosis are not the same thing! 

Ketoacidosis is a situation in which uncontrolled ketone production takes place. This is usually driven by a lack of insulin in the body (i.e. diabetes). Due to the low insulin secretion, blood sugar shoots up, and your fat cells release huge amounts of fatty acids. This triggers massive production of ketones, which, combined with the elevated blood sugar, messes with the acidity balance of the blood. This is dangerous and can even be fatal. Ketoacidosis most often only affects people with type 1 diabetes, who cannot produce any insulin. If your body can secrete even a tiny bit of insulin, ketoacidosis won’t happen.

Ketosis on the other hand is a healthy, controlled, and insulin-regulated process. It occurs in response to a reduced carb intake or fasting. Ketosis causes a mild release of free fatty acids and ketone body production. This process is natural and harmless and has many health benefits. In fact, when you awake in the morning, your body is often in a mild state of ketosis due to the absence of food and carbs during the night.

Thus, ketoacidosis and ketosis are vastly different. While the former is dangerous, the latter is harmless. Actually, ketosis is one of the best gifts you can give your body.