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Fat Adapted: The Beginner’s Guide to Fat Adaption on Keto


Do you know what it means to be fat adapted?


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Within this metabolic state, you’re able to burn your stored body fat reserves for energy. It can also reduce your body’s cravings for carbs. You may also feel more satiated after meals, which may result in eating fewer calories throughout the day, leading to weight loss.

But is it too good to be true?

To reveal the truth and dispel the myths, you’ll learn everything you need to know about being fat adapted in this guide.

What It Means to Be Fat Adapted

Most people are not naturally fat adapted. Instead, most people are “sugar burners,” meaning their bodies run off glucose for energy. This is because the traditional Western diet is heavily anchored in processed, carb-based foods[*].

But here’s the unfortunate cycle that carbs play on your body: When the supply dips too low, you’ll experience low blood sugar, which may bring symptoms such as lightheadedness, carb cravings, dizziness, an inability to focus, and a sugar crash. To stop the negative side effects and maintain sustained energy levels, your body needs more carbs.

Your body works overtime to combat this surge of glucose by sending out more insulin, a hormone to help sugar get out of your bloodstream and into your cells. Consequently, your insulin levels rise. When your insulin levels stay elevated, this is known as insulin resistance, which can lead to type 2 diabetes[*].

With too much insulin floating around in your bloodstream, your brain’s chemical signals are all thrown off, including those that let you know you’re full. This explains both why you tend to overeat and why you always feel hungry when eating a high-carb diet.

Your body craves more carbs and creates a downward spiral that leads to unwanted gain in weight and body fat. High insulin levels can cause a storage of body fat called visceral fat, which settles around your abdomen[*].

How to Know If You’re a Sugar Burner or a Fat Burner

To find out if you’re a sugar burner, answer yes or no to the following questions:

  1. Do you experience a “hangry” sensation (i.e., irritability when you’re hungry) when you go more than 4-6 hours without eating?
  2. Do you snack between meals, throughout the day, and into the evening?
  3. Are you having trouble feeling full or satiated after meals? (If you’re unsure, the next question will help you answer both.)
  4. Do you crave something sweet after meals despite feeling uncomfortable or bloated?
  5. Do you prefer carb- and sugar-rich foods like bread, pasta, cookies, or ice cream?
  6. Do you struggle to lose weight around your midsection?

If you nodded your head yes more than no to these questions, you’re most likely a sugar burner.

Don’t you think it’s time to switch to a better energy source? Becoming fat adapted means you’ll use excess body fat as a steady fuel source, rather than an influx of carbohydrates.

That’s fat adaptation in a nutshell.

Why Fat Adaptation Is Different

Your body is capable of metabolic flexibility, or switching between using sugar or adipose tissue (aka stored fat), to perform all its daily functions.

To get to the metabolic state of fat adaptation, you need to tackle three steps:

  • Limit the number of carbs you eat
  • Eat a larger portion of healthy fats
  • Monitor your intake of high-quality protein

By reducing your carb intake, your body will burn off all your remaining carbs and glycogen stores right away. Then it will tap into your excess fat stores to give your metabolism and energy a boost.

Combining protein and high fat will keep you feeling full and energized so you won’t experience energy crashes, midday hunger pangs, or unwanted sugar cravings. When you’re fat adapted, most people find themselves able to go 4-6 hours between meals without feeling hungry.

How to Become Fat Adapted

Fat adaptation is a simple way of saying that you’ve taught your body to burn fat — rather than glucose — for fuel.

Here’s how to do that: Slowly start reducing your intake of foods high in both carbs and sugars, and replace them with healthy fats and high-quality proteins. When you do consume carbs, consume foods with a high amount of dietary fiber. Eat healthy fats from coconut oil, MCT oil, avocados, and olive oil, and high-quality protein from grass-fed meat, seafood, and eggs.

Note that “slowly” is a key point here. Going from eating 100 grams of carbs to 10 overnight is extremely taxing on your body. Rather than cut carbs out cold turkey, which can cause negative effects including headaches, brain fog, nausea, and other symptoms known as keto flu, try a more moderate approach.


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To ease the transition period, take things slow and steady. Reduce carbs little by little, simultaneously adding in more healthy fats and protein to ensure you’re consuming enough calories.

How Fast Can You Reach Fat Adaptation?

Good news: Transitioning to a fat burning state can take as little as three weeks.

First, you’ll experience the initial phase: carb withdrawal. This phase might include the keto flu, which can last anywhere from 3-14 days. During this first week or two, your body is using up stored glucose, or glycogen, and is signaling you to replace them[*].

From there, you’ll shift into the second phase, which can last between 6-8 weeks. Here, your body really starts to make the transition from burning glucose to fat.

Once you’ve maintained this stage for several weeks, you’ll be in maintenance mode. That means your fat burning state will continue, as you continue to fuel your body with healthy fats instead of carbs.

How to Tell If You’re Fat Adapted

If you’ve been following a low-carb, high-fat diet for some time, you’ll want to keep an eye out for these signs that you’ve become adapted:

  • Are you able to go longer without eating between meals? Instead of only making it 2-3 hours after a meal before craving a snack, you should be able to go without food for 4-6 hours.
  • Are you experiencing consistent energy throughout the day? If you’re adapted, you should be experiencing fewer dips in energy because your fat stores meet your body’s energy needs.
  • Are you able to work out without having to fuel yourself with lots of carbs? Once you’ve reached fat adaptation, you’ll have all the fuel you need for intense training sessions and physical activity. If you’re an endurance athlete still relying on carbs as your primary workout fuel, you’re not adapted yet.

Answering yes to these questions means there’s a high chance you’re fat adapted and burning fat as your primary fuel source.

If you’re not fat adapted yet — despite following a low-carb diet — your carb intake may be too high for your body, or you might need to consume more fat or protein. Experiment with your macronutrient intake levels, and you’ll reach fat adaptation soon enough.

Some people believe using keto strips can help you determine your state of fat adaptation. Unfortunately, these don’t give you an accurate answer.

Fat Adapted vs. Ketosis

After reading the previous sections, you may be thinking, “Isn’t fat adaptation the same thing as ketosis?”

Short answer: Being fat adapted and being in ketosis are two different states.

Fat adaptation means you’re burning fat through fat oxidation[*]. A ketogenic diet — which means eating a mostly fat-based diet comprised of animal fats and high-quality protein — puts your body in a state of ketosis.

In ketosis, your body produces ketone bodies for energy in an attempt to use up fatty acids. When your blood ketone levels rise, parts of your body (like your brain) that normally use glucose will use these ketone bodies instead[*].

You can be in ketosis without being fat adapted, and you become fat adapted without being in nutritional ketosis. You don’t have to follow a keto diet to reach fat adaptation. Some people eat vegan, primal, or paleo diets, or try intermittent fasting to stay in this state — but they are not in ketosis.

Yes, this sounds confusing, but here’s the bottom line: If your body is not producing ketone bodies, you are not in ketosis. However, you could be burning fat stores through fat oxidation, which is a fat-adapted state.

Fat Adaptation and Keto Adaptation Are Not the Same Thing

If you’re just starting a keto or low-carb diet, you have probably heard the terms “keto adaptation” and “fat adaptation.” While these are two similar metabolic states, they are not one and the same. That said, you follow similar steps to get to both.

To become fat- or keto-adapted, eat a low-carb, high-fat diet aiming for a carb intake between 20-50 grams per day. This will help you transition from burning glucose (being a sugar burner) to burning fat stores (being a fat burner).

You can be in a fat adapted state without being in ketosis (keto adapted), and vise versa. If your body is not producing ketone bodies to use for energy, you are not in ketosis. You can, however, still be in a fat-adapted state through other means, such as fat oxidation or glycolysis.


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To learn more about a ketogenic diet, which gives you fat burning health benefits, check out this guide.


11 thoughts on “Fat Adapted: The Beginner’s Guide to Fat Adaption on Keto

  1. I am so glad that I signed up for this newsletter. Your recipes look delish and your articles are clear and comprehensive. Even though my husband and brother won’t be following this plan, I am sure that I can sneak in some of your wonderful recipes. Thank you.

  2. I am looking to lose quite a bit of weight I have been doing the “Keto diet” for going on 4 weeks and have lost 15 lbs even though that’s a great start I’m in the Army and need to lose a lot more! I ordered the bundle from you guys and I need more information! Do I go for fat adapted or ketosis I also order a smart scale and a keto mojo blood glucose meter I’m all in! Let me know about when to use your products!

  3. I came across this article when I was looking for an introduction for fat adaptation. The author is clearly an advocate of this approach and I enjoyed the blog. Now I’ve made plenty of typo mistakes in my time so I’m far from perfect, but when it came to trying to understand the technicalities of fat adaptation I was confused. I didn’t understand what the author meant by: “Fat adaptation means you’re using fat as fuel through fat oxidation and glycolysis, or using glucose as energy.”. Can someone break this down for me please?

  4. Read it again slowly. The author was quite clear and exactly correct. Great article. I lost 20lbs in 2 months on the keto and tons of belly fat despite having thyroid issues. It also virtually diminished inflamation caused by lupus and improved my overall health. (Female 62yrs. old) Thank you for this. I learned even more!

  5. Dr. Berg on youtube is a valuable resource! Check him out he is wonderful! Also check out “The Magic Pill” film and all the episodes of” Paleo Way”, they are both on Netflix. I think the film and also snippets of “Paleo Way” are both on youtube for free. This is a way of life and I’m so glad I found it. I feel great!…like I did when I was 20. I went slow, just got fat adapted the first month and then started to do intermittent fasting because it was so comfortable. It was easy no cravings or hunger. I kept watching Dr. Berg and healed my body with specific minerals, vitamins with food and/or supplements. I vary cardio exercise/muscle work, and longer fasts but I switch it up, not every day is high ketosis. I’m losing steady and slow. 🙂 And feel wonderful. Go slow.

  6. I have been in ketosis for 6 weeks now and the last couple of weeks I have not lost any weight I believe it has been long enough for
    Me to be fat adapted but I still get hungry about 3 hours after breakfast is there something else I need to do other things I need to try? The fasting does not quiet work well at this time I just get super hungry. I am currently 240 and I am 5 foot 8 inches 30 years old please help

    1. Hi, there are many factors that could be at play here. Are you having enough meals when it’s time? Are you getting enough sleep? Are you drinking enough water? Getting enough fiber and protein is also important.

  7. MyFitnessPal uses total carbs not net carbs. I use net carbs. You have to enter manually for correct carb counts.

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