My Case Study

It is not always clear what is meant when someone uses the term “Fat Adapted”. Based on my experience, I would like to explain what this term means to me, how to achieve it, and how to know you have achieved it.

Fat-adaptation involves eating a high fat, low carbohydrate (carb) diet in order for your body to use a greater amount of fat as fuel. Once your carb stores (glycogen in liver and muscle) are low your body then starts to produce ketones in a process called ketosis. Ketones, mainly beta hydroxybutyrate are produced from fatty acids and can supply our brain, organs and muscle with fuel so we don’t need to rely exclusively on glucose anymore as the main fuel source. So basically you re-train your body to use fat as the key fuel source. Fat adaptation can occur within a few days if you go with a very low amount of carbs (25-30 g per day [a small scoop of mash potato is around 10g] or you may opt for a longer time frame in which you allow yourself more carbs (less than 50 g per day).1 Once you are fat-adapted you can then experiment with adding in some extra carbs in order to develop your own tolerance level. There will be some trial and error and the longer you follow a higher fat lower carb diet the greater your ability to dip in and out of ketosis without it affecting your fat burning rate.

Our Bodies Are Always Using Fat And Glucose As Energy

The balance between using glucose as energy and fat as energy is what we are trying to change. In other words, we are trying to get our cells to more ably use fat as the primary fuel source:

• Eating a diet that is high in carbohydrates increases insulin levels.
• Increased levels of insulin stimulate using glucose as energy and storing the excess glucose as fat.
• Insulin inhibits our bodies from releasing fat from fat tissue and using it as fuel.
• By eating a high-fat diet and keeping carbs low, insulin levels stay low and fat is allowed to be used as the primary energy source.

What About Ketones?

In addition to using fat, another fuel comes into play when insulin levels are low—ketones. Just because we have low levels of insulin, and thus lower levels of glucose, and higher levels of usable fat (Ketones-the usable form of fat in the body), this doesn’t necessarily mean our cells can use the higher levels of ketones.

Like fat, ketones can be readily used as a fuel if cells (in muscle, brain, etc.) have sufficient mitochondria. The increased reliance on ketones as a fuel is another key feature of becoming fat adapted. The amount of ketones in our blood increases within a few days of eating LCHFMP. Once the stored levels of glucose are low and insulin levels stay, the liver begins making more ketones from fat. The period of fat adaptation that occurs in the cells takes at least 2 weeks, but can be closer to 4 (as seen in the cyclist study). Once this occurs, you are fat adapted—your cells have developed the capacity to use the extra ketones you are making and the fat you are releasing from fat tissue.

How Do You Know If You Are Fat Adapted?

Directly measuring your level of fat adaptation is simple, but not very practical. You could do a muscle biopsy and determine the number and size of your mitochondria, including measuring the levels and activity of the many proteins that facilitate the process. This is painful and expensive and I’m not aware of any doctor that would order this kind of test or a lab that would do it.
Another way to measure fat adaptation is an exercise stress test, which measures the gases exchanged in your breath while doing increased levels of exercise. This can be expensive but is a very accurate way to measure your level of adaptation. The stress test tells you the level of fat you are burning at any given intensity of exercise. However, there is a more practical way of knowing when you are fat adapted.
In the first few weeks after starting LCHFMP diet your levels of ketones will increase. This level of ketones can be measured. However, having high levels of ketones doesn’t mean you have adapted to using them. When you are fat adapted, you will notice a change in energy level. If you exercise regularly you will notice a feeling that you can keep going longer than normal. If you don’t exercise regularly, you will likely nevertheless notice that going up a flight of stairs is easier and you are not as tired from doing normal activities. You will start to feel spontaneous urges to do things that you normally avoided because they took too much energy. In other words, the best measure of being fat adapted is how you feel. When you are eating in a way to keep your insulin low, and thus allow your body to make more ketones and use fat and ketones for fuel, your cells adapt to more ably use these fuels and you will feel more energetic.

Conclusion

Know that the process of fat adaptation can continue for many months. The key is consistency. Eat in a way that will constantly keep insulin levels low (LCHFMP) and your cells will adapt to become very good at burning fat. You will feel an energy level you never thought possible.