There is much confusion in keto land about what all of this means and what the relevance is to weight loss. I will try to make it clear what these things mean, how they affect you and when they happen.
People often ask “How do I know if I am fat adapted?” or “How long does it take to become fat adapted?” or my favorite one from recently “When I am fat adapted does that mean I can carb up?”
First lets talk fat adapted.
I find this one particularly amusing. People assume they will hit some magical state where fat starts to melt off their body. This one is great; “When you are fat adapted you can eat less fat and your body will just eat away all your love handles.” Well in the ever so shortsighted of terms, it will. Then you will stall and be stuck for a good long time. There is no magic land where your body just decides that it will now use its stores of body fat as a primary fuel source. The body fat is meant for emergency fuel. Never for primary fuel and it will never be allowed to be used as such. If you cut your dietary fat down it will take from your fat stores to cover for the shortage in the short-term as it thinks that you are in an emergency shortage of food. If you continue to not eat enough dietary fat it will get wise to your treachery and shut you down. This is why 100% of people see a reduced loss week after week until stall city. That is not fat adaptation. That is just plain old caloric restriction. It doesn’t work in the long-term on a conventional diet and it won’t work on keto. There is no magic.
The truth is that we are fat adapted from birth. We are designed to run on fat and do so every single day of our lives. Well mostly at night but you get the drift. Whenever the carbs and protein are used up, we burn fat. We actually burn a bit of fat all the time no matter what. So we are already adapted to using fat as fuel. What people are getting at with this fat adapted term is actually more like being low glucose adapted. We are becoming better at running primarily on fat rather than primarily on glucose. The new state is not that we are getting used to running on fat or somehow now able to just magically use our emergency fuel as primary fuel, it is that we are getting used to not running on sugar. The reason we get more efficient at it and start to run better is because we are exercising the pathways that we don’t normally use, like Gluconeogenesis, and we are getting better and faster at fat oxidization. This is actually better deemed as metabolic flexibility.
When does this happen and how long does it take? This is a long process and I don’t know that it has an end. After more than a year being in constant strict ketosis, I still see performance increases. It is gradual and depends on how much you work the system much like aerobic endurance improves the more you work it.
Now Keto Adapted.
Again, we are all adapted to using ketones from birth. Babies actually flex in and out of ketosis all the time. Adults do as well. When you don’t eat for anything longer than 24 hours you will likely go into ketosis. If you do a severely caloric restricted diet you will likely go into ketosis. You can actually get into ketosis by eating a potato only diet. Strange but true. Ketosis happens when the body is in a state of inadequate glucose to feed the brain. This triggers ketone production to save the brain from energy crisis.
What people are getting at with this term is getting better at using ketones rather than glucose. This is again more about being metabolically flexible and exercising the pathways that are not commonly used when running off primarily glucose. It again is not some magic state that allows you to just burn off the body fat without regards to incoming food energy.
How long does this take? For some it is immediate and some it take a week or a few weeks. Most people think this is what it means when they get past the keto flu. I personally think this has nothing to do with keto flu. Keto flu is more about electrolyte imbalance and a withdrawal from carbohydrate metabolism.
Can you eat carbs and get back into ketosis once you are keto adapted or fat adapted?
This one I love. Actually I really hate it. If you are already looking for a way that you can eat all the carbs again and get back into ketosis fast, you are barking up the wrong tree. You are already looking ahead to failure. The ketogenic diet is supposed to be about optimal health. The anti-inflammatory properties, cognitive benefits and the weight loss are all directly related to not having inflammatory carbohydrates as part of the diet. If you are only just getting into this and already looking ahead to see if you can eat your precious carbs again, you are in the wrong head space.
With that being said, once you get to a place where you are comfortable with your health and weight, if a family event or vacation comes up, you can certainly eat a carb filled meal and not die from it. Will you feel ill or inflamed or gain any weight? Likely all of the above. You will recover from it quicker the longer you have been in ketosis. You will get back into ketosis more quickly than before and the effect of the carbs will go away faster than they did in the past. That does not make it a good idea or does it make it beneficial to put yourself in and out of an inflammatory state. So if you are planning on getting “adapted” then carbing up every week cause you can get back into ketosis in a day rather than 3-4 days, you will not be doing yourself any favors long-term and probably set yourself up for a slide back in the wrong direction.
Does getting back into ketosis faster after eating carbs mean you are fat adapted or keto adapted?
Ketone production really depends on one thing really. Liver glycogen. When we have stored glycogen in the liver the body will not make ketones and even one step further, the body will start burning them preferentially to clear them from the system. Those that get back into ketosis fast are those that have a fast metabolism and are metabolically flexible enough to be able to switch back and forth between fat metabolism and carb metabolism.
What does that have to do with getting back into ketosis faster or being keto adapted/fat adapted? The real factor that effects being able to get into ketosis fast after eating carbs is not being either of those things. It is about being insulin sensitive. When you are insulin sensitive, the body is very efficient at dealing with carbs. They body responds quickly at every turn. It sees the carbs and sends insulin out at just the right time and amount then shunts the glucose away to the liver and tissues quickly then clears the insulin fast. When insulin is cleared then the body will get back to using fat as primary fuel and it will use the glycogen (stored glucose) in the liver to maintain blood glucose and the brain will use it as well. There is only about 60 to 100g of glucose stored in the liver and this will not last long. Any amount consumed above that will have been stored in muscles and this is not a factor in returning to ketosis as it is saved in the muscles for intense activity and will not be used for anything other than that. You can still achieve ketosis with stored muscle glycogen. Only the liver glycogen affects ketosis. Once the liver is empty of glycogen, the body open once again to get back to making ketones.
Someone like me, who is now extremely insulin sensitive, I can eat 100g of carbs and be back in ketosis in several hours. How? I go to the gym and clear out the stored glycogen with intense training so as soon as my workout is done I am back to making ketones. Because of my insulin sensitivity, I don’t have elevated insulin blocking fat metabolism during or after the training.
The worst part about carbing up though is the fact that after eating low carb for any period of time we are phsyiologically insulin resistant and you will have very high blood sugar each time you carb up. This is normal and is meant to spare glucose during times of low carbohydrate availability. This prevents the body from making too much glucose via gluconeogenesis. If this didn’t happen the body would be burning through lean tissue at an amazing rate and that would be pretty bad. If one to were to return to eating carbs daily this insulin resistance would vanish and you would be back to a normal state as far as insulin sensitivity goes. Doing just random carb ups is actually dangerous as the elevated glucose will damage blood vessels and increase your risk of heart disease.
How does one get to be insulin sensitive?
This is not all that easy. Exercise increases insulin sensitivity probably better than anything else. Intense exercise especially. The only problem is that intense exercise also complicates weight loss. I won’t get into that right now though. Other things that increase insulin sensitivity is proper diet and time. Eating breakfast is another great way to express the genes responsible for insulin sensitivity. Usually once one gets to a healthy weight and maintains it for a long enough period they become more insulin sensitive.
This is why carb ups are not a great idea for the majority of people. Most people with weight issues are not insulin sensitive so they will not get into ketosis fast and will likely feel really bad after a carb up. They will go back to low carb and go through a period where they have neither proper glucose to fuel the brain or adequate ketone production to offset the low glucose.
So you see it has nothing to do with being “keto adapted” or “fat adapted” at all. It is about insulin sensitivity/liver glycogen and insulin sensitivity is something quite hard to come by. For the average person, don’t worry about “When do I get adapted so I can eat carbs” and just start worrying about being healthy. Forget about the carbs. They never did you any good in the past and they won’t do you any good in the future.
I hope this gives you a more common sense view of what it means to be “adapted”.
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