5 Signs That You’re a Fat Adapted Athlete

Fat adaptation is the metabolic reorchestration from a predominant fuel source of glucose to a predominant fuel source of fat. In other words, when you are fat adapted, your body can recognise fat as its primary fuel source rather than carbohydrate. This is the preferred metabolic state of the human.

The process of fat adaptation starts with JERF (Just Eat Real Food) and LCHF (Lower Carbohydrate, Higher Fat) and can take 8–12 weeks, but please keep in mind that this is highly dependent on the level of carbohydrate restriction and the individual at hand. To find out more about becoming fat adapted, read this.

One common question we get asked here at TNN is ‘How will I know when I am fat adapted?’ This is a very valid question so we thought we would share a few signs to give you some clarification on the matter and tell you if your body has reached a state of fat adaptation.

Our top 5 signs that you’re a fat adapted athlete are:

  1. You have stable blood sugar levels

Burning fat for energy will break the vicious cycle of the blood sugar rollercoaster, or the severe highs and lows that accompany a sugar-burning metabolism. This is often one of the first benefits observed with fat adaptation, and a sign you are keeping your insulin (our fat storage hormone) levels in check. The metabolic benefits of low insulin are many, including a body that is primed to burn, rather than store, fat.

  1. You have excellent satiety between meals

Can you go 5 hours without needing your next meal or snack? Appetite control is one of the many amazing benefits of fat adaptation. On the other hand, if you are always carrying a muesli bar or piece of fruit “just in case you get hungry”, then it is likely that you have poor blood sugar control, a sugar-burning metabolism and a body that is geared to store fat. We only need to look to our ancestors to see that periods without food are extremely healthy, but unfortunately our current constant supply of food, and incorrect education and media messaging around meal times and frequency, have us bound by our appetites and resorting to calorie restriction in a futile attempt to shift body fat.

  1. Elimination of the ‘hangries’ (hungry + angry)

The stable blood sugar created by fat adaptation can be quite life changing as you are no longer dependent on your appetite, or counting down the minutes until your next meal (or sugar fix). Too many of us experience the hangries on a daily basis and accept that it’s normal, when it’s a complete by-product of our previous meal choice/s. Shifting towards burning fat for fuel not only keeps blood sugar levels in check, but it prolongs energy and doesn’t leave room for mood swings and the hungry/angry feeling that comes with a sugar-burning state and the urgent need for your next fix.

  1. You can extend your overnight fast

The word breakfast can be defined as “the first meal of the day especially when taken in the morning”, however it really means “breaking the fast” and does not need to be at 7am (or any defined time of the day). Extending your overnight fast, and comfortably eating your first meal mid-morning (for example), is an excellent example of the capacity of a fat-burning metabolism. Please note: if you have always eaten breakfast at 7am you can expect to feel hungry at this time, but often it is ghost hunger as your body has been programmed this way over many years. Over time you can reverse this habit and the more you JERF/LCHF, the easier it will become.

  1. You have the ability to train in a fasted state for 2+ hours

If you can train effectively in a fasted state for over 2 hours, you are definitely fat adapted. A sugar-burner will use up their glycogen stores very quickly and therefore require an exogenous source to continue exercising beyond the 2-hour mark. When your body relies on fat as its main source of energy during exercise, there is more than double the amount of calories available (carbohydrates contain 4 calories per gram, while fat provides 9 calories per gram). This fat-burning ability also has a glycogen sparing effect, so that the carbohydrate stored in muscle is available to support high intensity activity (where it is most required). Please note: unless you are an extremely well fat adapted athlete we don’t recommend fasted training beyond 3 hours. There are also effective strategies that should be implemented so as to not become catabolic during this time.

Want to learn more? Let us guide you with our High Performance Fat Loss Program or Elite Performance Program, dependant on your body composition goals. As always you can book your complimentary 15-minute Skype consultation here as we would love to guide your fat adaptation journey.


  1. Noelle

    This is SUCH an interesting read as I’ve always had a very low appetite and always naturally engaged IF without knowing what it was. Unfortunately this lack of appetite meant I’ve severely damaged my metabolism as I’d forget to eat until 3/4pm some days (stress dependent) and frequently ingest much lower calories despite being whole foods and LC, they were also LF. It’s so difficult to know where to tow the line with IF when you need to be reminded to eat. Excellent site, wish you the best of luck with TNN Steph!

  2. Min Benstead

    Hello Noelle, thank you for your feedback. If you’d like to chat further with us about this we do offer a complimentary 15 minute skype consult, you can book this in here.

  3. Mike Kim

    Great article! I’ve been toying around lately with IF.. its a little tough getting used to, but it’s coming along… no hanger issues at all! Now it’s time to try training for long periods in a fasted state! Oy!

  4. Di

    I started this journey with Steph at TNN and love the change I am experiencing on my long runs. I run without any gels or glucose and have not experienced hitting the wall so to speak ever since following a JERF lifestyle. It’s awesome not having the cravings for sugar or sweet food and the energy and how good my body feels. I haven’t been sick and I put it all down to what I put into my body.
    Thank you Steph!!

  5. Min Benstead

    Wow Diane. What amazing results, you must be feeling awesome!

  6. Brent Gremillion

    Thank you for this article. Great info. I’m attempting to become a fat adapted cyclist. I had a 4 hr. ride this past weekend and totally crashed at the 1:30 mark. I had to limp home and get off the bike after 2hrs. Also, I seemed to have an abnormal amount of sweating. As if my body was completely ridding itself of water. Is this normal? Are you saying that I’ll know when I’m fat adapted when I do not experience the crash and I’m able to sustain my energy on long rides?

  7. Min Benstead

    Hello Brent, sustained energy is a great indicator. We’d love to chat with you further and do offer complimentary 15 minute skype session, you can book in here.

  8. Alan

    Can I ask why you don’t recommend training past 3 hrs unless being very fat adapted?

  9. Steph

    Hi Alan, you can become catabolic and start to negate performance and recovery.

  10. Mostafa

    Hello Steph,

    Great article! Thank you very much. I have a few questions though, First, don’t you still need to eat a low carb diet if you’re fat-adapted? And, how much carbs can eat and still be able to go back in ketosis? Also, Can you cycle your carbs on training vs non-training days? Second, what are the measures that one should take so as not to be in a catabolic state when training-while-fasting? Also, is powerlifting and/or resistance training compatible with the low carb diet? And finally, can you actually build muscle on a low carb diet?

  11. Min Benstead

    Hello, your carbohydrate intake needs to be tailored individually and is highly dependent on your energy expenditure and the type/amount of exercise you are doing. To answer your questions tailored to your training and desired outcomes, please book in for a consultation here.

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