Within the first week of starting a low carb, ketogenic or animal-based diet, people often notice a rapid weight loss of about 10 lbs, increased energy, lessening of anxiety and depression, along with less hunger and carb continue on with the protocol.

This is why most who begin this way of eating think it is simply GREAT and have no problem continuing it.  But there’s more to come! Once you’ve been in ketosis for 3-6 weeks you get the additional benefits of being fat adapted!  

You may have heard the term “fat adapted” or have even been striving for it. After all, becoming fat adapted is the goal on a low carb diet because it means your body has completely transitioned from relying on carbohydrates for fuel (or being carb-adapted) to relying on fat as your primary energy source (aka fat adapted).

What Exactly Is “Fat Adapted”

Being fat adapted, or keto adapted as it is sometimes called, means that your body has fully adjusted to running on fat instead of carbs as its primary fuel source. 

Babies are born in ketosis

Being in ketosis and using ketones is the natural state that you were born into. During the 3rd trimester, even when the mother is not following a ketogenic diet, the body will produce ketone bodies which are utilized by both the mother’s and baby’s brains.  Studies show that babies who are breastfed, slip in and out of ketosis easily, and most breastfed babies are in ketosis.

Once babies wean, whether onto formula or carbohydrate-rich food, their body begins to use glucose as the primary fuel source for their brain and energy.  This is simply the body becoming used to running on carbs. If babies wean onto a low carbohydrate diet, they will continue to prefer using ketones for energy and their brain even if they occasionally eat sugar-containing fruit or other food. 

Carb Adapted vs Fat Adapted

People are either carb-adapted (most people in the Western world) or fat adapted (those following a lower carb diet).  The body can effectively use both methods for energy and to feed the brain, however, after a lifetime of eating a carbohydrate-rich diet, the body will be conditioned to expect these carbohydrate fuel sources more than fat.  By becoming fat adapted, you condition your body to prefer fat over carbs for fuel. 

Why Become Fat Adapted

When you are fat adapted, you are no longer reliant on consuming carbohydrate regularly to feed your brain and muscles. Instead, your body is already in the state of burning fat so it can switch with ease from burning dietary fat (fat that you eat) to fat that is stored in your body.   

Body Fat Burning Preferred 

Even at a healthy weight, being fat adapted is beneficial because the body always has food on board – if it needs more energy to run a marathon or just complete errands before lunch time, the body can seamlessly tap into stored body fat. 

When you are fat adapted, you may feel hungry, but you won’t get ravenous hunger/light headedness that often accompanies being carb-adapted and hungry. 

By contrast, if your body is used to eating carbs and prefers burning carbs, it is common to get hangry (grumpy from hunger) due to hormones that are telling you to eat those carbohydrates SOON. 

Insulin & Carbohydrate Metabolism

Insulin is also released regularly in those who are carbohydrate adapted, because the body expects to have to digest carbohydrates.  Insulin has a number of functions, but two of the notable ones are t

·       Causes hunger

·       Lowers blood sugar levels. 

When you are in a consistent carbohydrate-burning state, as most of those following a standard Western diet are unless you have intentionally been lowering your carbohydrates, your body will secrete insulin when it assumes you are going to be eating carbohydrates.  If you are eating ‘small frequent meals’ with carbohydrates, insulin will be secreted consistently throughout the day.

Insulin Makes You Hungry

The problem with too much insulin is that insulin makes you hungry.  When insulin is kept high, you feel hungry even if you are eating sufficient calories to maintain the functioning of your body.  If you have a significant amount of insulin floating in your blood stream, it is going to make you hungry all day long! 

This is an appropriate biological response because insulin also lowers blood sugar. This means that if your body is producing lots of insulin because it thinks you are going to eat carbohydrates, you then NEED to eat or your blood sugar can drop too low. 

Insulin Lowers Your Blood Sugar

Insulin works to lower your blood sugar, by transporting the carbohydrates out of your bloodstream and into your cells. This is necessary even on a low-carbohydrate diet and everyone has a need for insulin.  The problem occurs when you need LOTS of insulin to digest carbohydrates that are eaten regularly and often. This can result in getting lightheaded or shaky or ‘hangry’ when you fail eat for a significant period of time.  

When you are fat adapted, your body will still secrete small amounts of insulin, but it these are insufficient amounts to cause light-headedness and grumpiness. Your body secretes just enough to keep your blood glucose within the correct ranges. 

Fat adapted might sound like a great place to be, so how do you know you are truly fat adapted? 

Signs You Are Fat Adapted

If you’ve consistently been following a low carbohydrate, keto or animal-based meal plan or program and been in ketosis (without cheats! You’re only cheating yourself) for 6-12 weeks, you are likely to now be fat adapted.  That means your body stopped the insulin roller coaster and is using fatty acids and producing ketones for energy all day every day.  

When you start a low carbohydrate diet your body is still thinking that it will be getting carbs imminently, and will switch back to carb burning if you eat a carb-heavy meal or more than 25-35 grams of carbs a day. 

Once you are fat adapted, you can eat ‘off plan’ for one meal every now and then (not every week) and your body will continue using fatty acids and producing the beneficial ketones for you, even if you just ate carbohydrate heavy foods. You are now a default fat burner! Keep up your protocol the majority of the time, and you will remain fat adapted. 

Some markers that you may have reached this fat burning state include:

1. You Have Endurance

When you become fat adapted your endurance increases because you are bringing your own personal supply of fuel right on your body along for the ride (or run or hike or whatever your endurance activity looks like)!  You may find you hit the ‘runners high’ faster and more often whilst eating this way, as your body has now adapted to go and go and go by running on fatty acids and ketones.  

2. You Can Skip A Meal

When you are fat adapted, your body prefers fat as a fuel source and is not secreting insulin to prepare itself to eat lots of carbs on your regular schedule. This means your blood sugar will not drop too low due to the excess insulin, and you still have plenty of fuel to keep you going until your next meal.  Being able to go hours beyond when you would usually eat is a sign that you are fat adapted.  You may have some hunger, but you are not becoming grumpy or getting lightheaded due to low blood sugar. 

Fat is also more nutrient-dense than carbs. Fats contain nine calories per gram, whereas carbs contain four calories per gram. Fat also contains fat soluble vitamins A, D, E, and K. When your body gets the nutrients it needs from fat, you feel more satiated with less food. Ketones also boost cholecystokinin, a hormone that keeps you feeling full. Consequently, you need less food throughout the day to stay feeling energized.

3.  High Carb Indulgences Have Less Of An Impact

During your first 30-90 days, it is important to adhere to your plan so that your body can fully transition into fat-burning mode. If you do veer off-plan, you will probably notice that you are kicked out of ketosis within hours.  After you become fat adapted, your body is used to constantly using fatty acids and producing ketones and it continues to do so – even if you have some fruit salad at a potluck, or some cake at a wedding.  

It is important to note that individual tolerance for eating off plan will be different and experimenting will allow you to assess where your personal threshold lies. This is ONLY after you are fully fat adapted!

4.  Your Ketone Readings Are LOWER

When you start on a low carbohydrate eating plan you may be testing your ketone level with ketone strips.  These strips monitor the number of ketones that are in your urine (or sometimes blood).  In the beginning, as you are becoming adapted to this new lifestyle, you will most likely produce very high readings! This is because ketosis and fat burning are uncommon states for your body due to years of high carb eating and your body is unsure  of how many ketones you may need to keep your brain fed. The liver then over produces ketones to make sure your needs are met.  

Once you are fully fat-adapted and your body has had time to adjust how many ketones you actually need, it stops producing as many ketones. This has nothing to do with how much fat you’ are burning. Burning more fat does not equate to making more ketones.  Where you once read ‘high’ ketones, you may only read moderate when you are fat adapted because that is all you need and you are using them efficiently. 

5. Better Sleep

One amazing sign you are fat adapted is starting to sleeping better and waking up feeling more rested. Studies show that the deep phase of sleep, called phase four, is lengthened on keto. Researchers theorize that this might be due to the affect keto has on adenosine in your brain. Adenosine promotes this deeper slow-wave sleep. 

6.  You Smell Good Again

The less than lovely side effects of low carbohydrate diets include your body excreting the excess ketones that it’s making during the adjustment period in some way. These are removed as acetone and you will definitely smell them in urine, breath and sweat. Thankfully, once you are fat adapted, your body produces way less ketones, and there is way less smell. 

Tip: During the adjustment period if you notice your breath or sweat smells too much, drink more water. Drinking water flushes the ketone by-product into your urine, where you can simply flush it out. If you are not drinking enough water it will come out your sweat or lungs. 

When embarking on a low-carb eating, becoming fat adapted definitely takes time, but it is worth the effort. Once you get there, you can reap all the amazing health benefits of low carb living.