keto adapted versus fat adapted

Keto adapted versus fat adapted

Since these two terms are used frequently and interchangeably, let’s examine what they actually mean. Then you can better determine which one you’re interested in. Although these two terms have a lot overlap, they aren’t exactly the same thing…


Fat adaptation: ‘The metabolic state of being able to effectively utilise and burn fat’.

Keto-adaptation: ‘The physiological process whereby your cells have adapted to using ketones and fatty acids for fuel’.

Fat adapted

Becoming fat adapted does not require you to be in nutritional ketosis, it simply means that you can tap into stores of fat, break down the fat, and use it as a source of energy. We all have the capacity to do this. The more readily/easily you are able to switch between using either of the two fuel sources, carbohydrate and fat, is termed ‘metabolically flexible’.

Babies are actually born in a state of nutritional ketosis, and utilise ketones and fat very efficiently (1). However, over a period of time, depending on your diet and lifestyle, the body can become less metabolically flexible – so less able to switch between using both fat and carbs as a fuel. Check out Introduction to the ketogenic diet to find out more about nutritional ketosis.

This is because dependent on your long-term diet and lifestyle, your body begins to build a set of machinery to better equip itself to deal with what you’re giving it. Hence, if you feed it lots of carbs and are not very active, it tends to build the machinery to use carbs but at the same time, it reduces the machinery to utilise fat for fuel. This makes it tough when you are trying to lose fat!

Benefits of being fat-adapted

It’s good for your health! You are likely to be metabolically flexible, which is associated with better health – being metabolically inflexible is associated with chronic diseases like type 2 diabetes (2). It also means that you are readily able to access your fat stores which means that you are likely to be at a healthy weight or readily able to lose weight. It can also be beneficial for the endurance athlete: check out The benefits of the ketogenic diet for the athlete.


Requires you to both be in a state of nutritional ketosis and also sustain this for a certain period of time. This means producing ketone bodies, on average between 0.5-5 mM for usually a minimum of > 6 weeks (3). Depending on you and your genes, as well as other factors, such as long-term diet, how sensitive you are to insulin already, training and health status, will determine both the extent to which you become keto adapted and how quickly this process takes place. The duration for which you are in nutritional ketosis is associated with influencing the extent to which you become keto adapted (3).

In order to get into nutritional ketosis you have to both reduce your blood sugar (glucose) levels sufficiently and reduce liver carbohydrate (glycogen) stores, which usually requires reducing your carb intake < 50g per day (or fasting and / or exercise) to make enough of these ketone bodies. This is different to fat adaptation which does not require this.

The benefits you may gain from being keto-adapted or how keto-adapted you are, will vary according to the duration that you are on the ketogenic diet. For instance, studies show that athletes who have been on the ketogenic diet > 6 months have adapted to be able to recover their muscle glycogen (carb stores) levels at the same rate as athletes on a high carb diet (4). However, this isn’t the case for athletes who go on the ketogenic diet for 4 weeks.

Also, by being keto-adapted, you gain the potential benefits of ketone bodies….

Benefits of being keto adapted

You get the benefits from being fat-adapted with the additional benefits of ketone bodies. Check out Pros of the ketogenic diet – other potential health benefits include improving the defence system of your body (improved inflammatory balance and antioxidant defences), as well as improved brain health.

Similarities between being keto and fat adapted

  • Both require your body to build machinery to break down and effectively and efficiently utilise fat – from fat you’ve eaten and fat stores.
  • Both result in increased metabolic flexibility, insulin sensitivity and capacity to lose fat.

Differences between being keto and fat adapted

  • Being keto adapted requires you to be in nutritional ketosis for a period of time (> 6 weeks).
  • Being keto adapted means that you gain the potential benefits from ketone bodies: anti-inflammatory effects, increased antioxidant defences, neuroprotective effects.

Final words

  1. Understand your current status and objectives: what your goals? Are you currently fat-adapted? Are you looking to lose fat? Are you looking to improve overall health? What kind of foods do you function best on? How do your objectives fit into this?
  2. Flexibility is associated with health: sometimes this flexibility has been lost and we’re moving away from the positive health markers, this can be the ideal time for a focus on nutritional ketosis temporarily, in order to readdress the balance.
  3. Check out the Introduction to the ketogenic diet and Pros of the ketogenic diet to become better informed about the ketogenic diet to see if it is something that interests you!

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This article was written by Antonia Osbourne.
You can read more of Antonia’s articles and learn about her specialist areas and experiences using the link below.
More about Antonia


  1. Platt and Deshpande (2005). ‘Metabolic adaptations at birth’
  2. Goodpaster and Sarks (2017). ‘Metabolic flexibility in health and disease.’
  3. Phinney and Volek (2012). ‘The art and the science of low carbohydrate performance’
  4. Volek et al. (2016). ‘Metabolic characteristics of keto-adapted ultra-endurance runners’

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