If you’ve been on a ketogenic diet for a while, you’ve surely heard the term “fat adapted” (also sometimes called “keto adapted”) or have even been striving for it. After all, becoming fat adapted is the goal on a ketogenic 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 or keto-adaptation).
When you start a keto diet, you’re retraining your cells to reach for fat stores (i.e. body fats, which are converted to ketone bodies) rather than glucose. Once that process begins, you’re on your way to becoming fat adapted,
But it doesn’t happen overnight. According to keto expert and New York Times best-selling author, Dr. David Ludwig, it can take two to three weeks or longer to become fully fat adapted depending on your bio-individuality and how strictly you adhere to a low-carb, moderate-protein, higher fat diet. (Go overboard on your grams of carbs per your specific ideal daily macronutrients and you will have a harder time reaching a fat-adapted metabolic state.)
The incentive to hang in there is significant. Once fat adapted, you’ll be able to go much longer between meals without feeling hungry, have much more stable energy throughout the day, and, if applicable, begin to mitigate some health challenges, including diabetes, migraines, obesity, and more.
So, how can you tell if you’re fat adapted? Let’s first understand the difference between ketosis and fat adapted.
The Difference Between Ketosis and Fat Adapted
Ketosis and fat adaptation are not the same. When you fast, embark on intermittent fasting, or cut way down on your carb intake for an extended period of time, your blood sugar and insulin levels drop. With an absence of carbs (sugar) to rely on for energy, your body, instead, reaches for fat and converts it to ketones to use as its fuel source. This is known as ketosis.
If you eat in a way that ensures a state of ketosis for an extended amount of time ̶ several weeks or more ̶ your body fully shifts to burning ketones for energy instead of glucose. When this happens, you’re fat adapted; so, fat adapted means your body has become used to regularly relying on blood ketones for fuel and no longer seeks carbs.
If you’ve been following keto for a few weeks and want to know if you’ve become fat adapted, here are the top seven signs to look for:
7 Common Signs That You’re Fat Adapted
Decreased cravings between meals
Fat adaptation influences your hunger hormones. Ghrelin, the main hunger hormone, is decreased when you’re fat adapted. This makes you want to eat less often and stop craving snacks between meals.
High-carb diets can make you tired. You burn through blood glucose quickly and consequent blood sugar spikes and plummets create feelings of fatigue. When you’re fat adapted, you are on a fat-burning diet and have stable energy levels throughout the day, which means you experience more energy and less fatigue.
Feeling satiated with less food
Fat is 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. Another reason you feel full 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.
Heightened mental acuity
Ketones, which were first used medically for the treatment of epilepsy are neuroprotective (protect nerve cells from damage). When you’re on a high-fat diet and fat adapted, you start to experience increased brain health. Some of these benefits include less brain fog, better focus, improved cognition, and increased feelings of well-being. In other words, you feel like your brain is functioning better overall.
Increased fat loss
When you go from being a “sugar burner” to a ketone burner, one of the quick side effects is loss of water weight. But by the time you’re fat adapted, your liver is used to converting fat into blood ketones for fuel. Increased fat intake lowers insulin levels. Insulin is a hormone that tells your body to store fat, so with less insulin, less fat gets stored. This means you continue to lose fat! Many people start keto because of the weight loss benefit.
One amazing sign you’re fat adapted is you’ll start 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.
Increased endurance with physical activity
When you’re fat adapted and exercising, you leverage fat instead of glucose for energy. This is particularly important because every body has limited access to glucose at any given time, and a glucose-driven body has a hard time quickly switching from reaching for glucose stores to reaching for fat stores; this is why endurance athletes relying on high-carb energy need to refuel in the middle of their activity; otherwise they “bonk” or experience an energy crash. When you’re fat adapted, you have easy access to a much greater energy supply – fat – which allows you to maintain more energy and exercise longer.
The Benefits of Being Fat Adapted
All of the signs above are great benefits to being fat adapted. But there are even more benefits:
You can explore your carb edge
When you’re fat adapted, you can experiment via food and ketone testing to find out your own personal daily carb limit. Some people are able to stay in ketosis while eating 20 grams of net carbs per day, while others discover they can eat more carbs yet stay in ketosis and thus fat adapted. Find out how to test your carb edge here.
You can cycle in and out of ketosis with greater ease.
Once you’re fat adapted, it’s easier for your body to transition in and out of ketosis (metabolic flexibility). This means that should you happen to overdo carbs every now and then but quickly return to eating healthy fats (like good-quality animal fats, coconut oil, and olive oil) and moderate protein, you can more easily transition back into ketosis, likely without experiencing the keto flu symptoms that newcomers face.
Unhealthy cravings disappear.
When you stop craving sugar and carbs and feel more satiated, you’re no longer battling against intense cravings for sugary/carb-heavy foods that aren’t good for you, so you’ll likely make better food choices, focused on healthy fats of course. This means you’ll get more nutrients and feel better all around.
The Final Word
When you’re on a high-fat, low-carb diet, fat adaptation takes time, but it’s worth the time and effort. Once you get there, you can reap all the amazing health benefits of keto living.