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Keto 101

How Do I Know If I’m Fat-Adapted?


In order for your fat-burning bod to gain full reigns, it needs to make the official switch into a fat- or keto-adapted state. Meaning your body has learnt to use fat as its primary source of fuel instead of depending on glucose (carbs).

To reach this metabolic state you need to ditch the carbohydrates from your plate and replace with lots of healthy fats, a moderate amount of quality protein and then just the small number of carbs (about 20g a day) for dietary fibre will come from leafy vegetables grown above ground.

Being fat-adapted means that your body knows 100% that fat is its preferred fuel source. It has built up the enzymatic and metabolic processes to effectively burn fat for energy; you can burn the fat on your body, you can burn the fat in your food and you can switch over to sugar-burning quickly (if you’re in Italy and really fancy that authentic pizza!) but then get back to burning fat. While you can be on a keto diet from day one, the fat adaption process can take 2 to 6 weeks, it totally depends on your body.


Once you’re eating keto, your ketones can start registering pretty soon; 3 or 4 days in you’ll likely start to register ketones if you’re testing your blood. Although your ketones are registering, your body doesn’t yet know that fat can be its primary fuel, it’s figuring out its new metabolism. Whereas once you’re fat adapted, you have both high ketones, and your body knows fat is its main source of energy.

You can achieve ketosis without being fat-adapted; this happens in the early stages, when you first start out eating keto and you’re removing the carbs, depleting the glycogen stores and replacing them with an abundance of healthy fats which metabolises into ketone bodies within about 3 days (for some people).

You can achieve fat-adaptation without being in ketosis; just following a low-carb / high-fat diet can steer you into becoming fat-adapted. The key benefit of the ketogenic diet is to produce ketones as a supplementary power source. Some people can be in ‘maintenance mode’ consuming a reduced amount of carbs that’s not quite as low as the keto way of eating so does not produce ketones bodies, but fat is still the main source of energy being used.


So, you’ve started keto, you’re in ketosis and you want to be fat-adapted like yesterday, AMMI right? I get it, you’re in the zone and ready to kick butt, but it’s going to take a little longer than that. Let’s break it down into each phase.

Phase #1: carb withdrawal. Not the prettiest phase as this rears it’s ugly head in the form of ‘The Keto Flu’, and can last anything from 3 to 14 days (in extreme cases, one month at most).

Phase #2: metabolic switch. This can last 6 to 8 weeks depending on an individual’s metabolism, but here the body really begins to make the switch to burning fat instead of burning glucose.

Phase #3: maintenance mode. This happens when you’ve maintained a fat-burning state for a several weeks, your body has gained the ability to put fat-burning on autopilot, providing healthy fats carry on fuelling your body instead of carbs, and you’re in maintenance mode.

Here are a few tell-tale signs you’ve officially made the full transformation from the traditional sugar-burning bod into a bonafide fat-burning machine.


These signs are a little different for everyone, but here goes:

  1. You’re able to skip meals without getting angry, hungry, hangry, punchy – whatever you want to call it 😉.
  2. You can go three, four, five or even six hours without a snack and also not get hangry.
  3. You don’t get ravenous, a feeling of intense hunger e.g. if you don’t eat in the next hour the world will end.
  4. You prefer high-fat foods over carb foods.
  5. After exercising, especially long distance aerobic exercise, you don’t feel the need to replenish yourself as much as you used to & you won’t be dealing with plateaus anymore.
  6. You feel copious amounts of energy. You feel a lot clearer about your energy, it will feel pure and good.
  7. The energy you experience should be pretty even all day, no afternoon lulls and you’ll go through the evening without feeling totally exhausted and then have a rested sleep.
  8. Your thoughts will become lighter, feeling less bogged down by emotional stress. Your brain feels able to cope with stress a lot better being fat fueled.

Sophie Laura

Hi! I'm Sophie (Easy Keto Lifestyle). I'm a Certified Nutrition Coach and I help women who struggle with their weight to radically transform their health and body, by living a simple yet delicious ketogenic lifestyle.

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  1. According to your list I should be fat adapted. I started Keto with dietdoctor.com May 21 and lost 7# first two weeks. Continue eating Keto woe but stuck at the 7#. Which goes up and down a pound or two. I do train 3x a week with a trainer for strength and balance. I am 71. Never hungry and have more energy than I know what to do with. Any other suggestions to get me losing? Also do IF and carbs under 20grams.

    1. Hi Carol, sounds like you’re doing great! How long have you been eating keto? How much are you wanting to lose? Have you been measuring your body as well as weight? You could be losing fat but gaining muscle from the training, which is definitely the best way, but it’s not showing up positive on your scales and that’s the only way you’re tracking.

  2. I’ve been doing what I need to do to stay in ketosis, eating less than 20 carbs on those days sometimes less than 10. Yesterday I ate less than 10 and pounded water and vitamins. Today I woke up starving. Is that because I restricted carbs so completely? I am 35 days into this new lifestyle and really enjoy it. The single downfall is that I’m tired quite a bit in the late afternoons. I am losing about a pound a week sometimes 3. My total weight loss is 18 lbs I’m guessing I’m somewhere slightly before fat adapted?

    1. Hi Sandra, are you making sure you’re eating enough fat throughout the day? Great that you’re keeping your carbs so low, but it’s reeaally important to be eating lots of fat until you feel satiated (don’t force yourself to eat, just eat enough to feel full), and moderate your protein – have you used our post on how to calculate macros, and track them using an app?

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