How long until you are OUT of being fat adapted?

(Todd) #1

I’ve been on my Keto journey since late January and have been ramping up triathlon training (which is subsequently on hold due to a knee injury) in the last 2 months. I was fully fat adapted and seeing the benefits of it both in weight loss and focus/energy. I’ve been cycling nearly every day a minimum of 13.5 miles (commute to work) and a max around 65 miles to this point, and lifting weights every other day. Over the last 3 weeks I’ve fallen off the wagon to the tune of 75-150g of carbs a few days a week with some days peaking at 200g. I’m critical of myself and commit to getting back on the horse each time I slip and have absolutely no problem following up one of these days with a 24-30 hr fast with no energy issues or hunger pains. I’ve put on about 4 lbs as well.

So my question is - How long does it normally take for your body to revert back to being a glucose burner if I’m not in Ketosis (<20g carbs/day)? I understand everyone is different - so give me your experience.


Instantly, if you take a huge load of carbs, your body will 1) replenish glycogen stores, 2) Immediately burn glucose for fuel because of the insulin spike.

But, its like riding a bike, once your body has become fat adapted (probably the first time in its life eating the S.A.D) it’ll know what to do once glycogen is gone and insulin is back down.


It doesn’t, our bodies will ALWAYS be able to chew through glucose at the drop of a hat!

(Todd) #4

So yesterday, for example, I fasted from 6pm the night before to 11:30 when I had a full hamburger (bun, ketchup, onions), some fries and water to drink - Probably 200ish grams of carbs. I rode my bike when I got home around 5:15pm for 2:26:01 getting about 44.4 miles and managed my HR to keep it as much in Z2 as I could. When I got home I ate 1 bs chicken thigh, 4 strips of bacon and half an avocado.

I typically won’t eat the fries but these are the shoestring kind which are a weakness. Based on this am I kicking myself so far out of ketosis that my body isn’t fat adapted anymore? I don’t have any issues with endurance or power later in my rides or climbing.

(Old Baconian) #5

@TMoran lfod is right, “revert” is the wrong word. Dr. Phinney explains that a significant level of glucose in the bloodstream is a metabolic emergency, and the excess needs to be cleared from the blood as quickly as possible. So insulin rushes to the rescue, telling muscles to burn it and fat to store it. He likens the process of fat-adaptation to climbing up a sand dune, and getting back to sugar-burning to falling back down to the bottom. The former is laborious and drawn-out, the other quick and easy.

(Todd) #6

Thanks for the insights. I’m still trying to understand the ins and outs of all of this. I’ve had it in my mind that I can have a little more carbs than 20g and I could get out on my bike and take care of the excess and still be fat adapted.

Now I’m kicking myself that I’ve let it slip this much and wondering what kind of gains I’d be experiencing being completely ketogenic and cycling for 2+ hours…

(Old Baconian) #7

Twenty grams of carbs is something of an arbitrary number. It’s a level of carb-consumption guaranteed to put practically anyone in ketosis. I read a comment by either Richard or Carl to the effect that they really wanted to say 0 g, but felt that probably wouldn’t go over well for most people, lol!

Depending on your biology, you may very well be able to eat more than 20 g of carbs a day and still remain ketotic. In fact, Dr. Phinney talks about anything under 100-125 g as being “low-carb” and talks as if lots of people get into ketosis eating that much. There are also people, about ten percent of the population he says (IIRC), who can eat all the carbohydrate they want and never become insulin-resistant (not me, however—that’s for sure!). So biology counts for much, here. So don’t worry too much about your carb level, unless you notice ill effects if you get too lax.

One last point to clear up: the way to get glucose out of your bloodstream is to secrete insulin, so that your fat cells are signaled to store it and your muscles to burn it. Exercise won’t help with this. So since the point of a ketogenic diet is to lower insulin, be careful with your carbs. Just don’t freak out if you go over your limit (whatever it is). Simply KCKO.

(Autumn) #8

I know this is an old post BUT I just have to add in on this in case you ever went back to the post and still wondered the same thing. Have you ever considered that your body is burning ample amounts of calories than you are actually taking in? I am almost willing to bet that when you are giving yourself the carbs you are ( and exercising the way that you are ) that your body is actually storing the carbs and turning it into muscle mass. That might be the 4lbs you have gained so drastically.

It looks to me as if you are working out way more than you are eating. That can cause two different things to happen when you eat carbs. Your body is either breaking down the source of carbs for energy causing your muscles to tear and rebuild quicker than if you were just keto OR it is freaking out thinking it is in some type of starvation mode and hanging on to everything you ate in case you don’t get it anymore.

I am not a doctor or anything close to it lol but that is just a thought I wanted to add.

(Old Baconian) #9

Carbohydrate cannot be turned into muscle mass. To build muscle you need protein, especially protein that contains branched-chain amino acids. Amino acids contain nitrogen, whereas fatty acids and carbohydrates do not, so without a source of nitrogen, there is no way to build muscle proteins. This is why protein is essential to the human diet.

While eating carbohydrate does not cause muscle gain, it does promote water-retention, and that is more likely to have been the cause of the weight gain.

(Alec) #10

I am not sure we really answered the title question here. It is the question I am interested in answering. Not whether we would burn glucose if we ate it, but how long does it take of regular carb/SAD diet to lose fat adaption, so you have to go through the fat adaption process again?

I am asking because I am doing my first 36 hr fast for a long while, after a bit of a rough patch diet-wise, and I am doing it really easy. No hunger, no cravings, nothing. I am almost thinking I might extend it a little tomorrow. We’ll see how it goes tomorrow.

But how long does it take to lose fat adaption?

(Old Baconian) #11

I don’t think anyone knows. We can switch back into metabolizing glucose at any time, but you’re asking how long it takes to accumulate enough mitchondrial damage for the metabolic switching to get stuck in glycolysis again. If I had to guess, it would be probably longer than a month, but less than a year.

(Ken) #12

I see we’re “Rediscovering the Wheel” on this one. This topic has been discussed in Bodybuilding/Fitness groups for decades. Detrimental readaptation that recreates anorexigenic hormonal resistance states is dependent on one thing. The recompensation and subsequent chronic overcompensation of glycogen. Same thing with fat gain. It’s only after glycogen is full that the receptors are desensitized that the body begins directing glucose into lipid cells for storage. This is also why you can eat occasional carbs for metabolic purposes with no worries of fat gain. As long as you eat them when glycogen is depleted. Fat gain and adaptation doesn’t happen unless glycogen is full. It’s merely the opposite for fat loss, glycogen has to be depleted to begin lipolysis.

Carbs have long been known to.assist protein transport into the muscles. That’s why limited amounts are consumed around workouts.

Back to the original question. It depends on how much and often you overcompensate glycogen.

(Joe D) #13

I really hate to ask questions that have probably been answered a million times but I’m fairly new to this. I feel like I’ve done my homework and everything seems to be working. I test ketones almost daily and have had positive readings pretty much since I started. I’ve been strict and I’m happy with results so far… however!

No matter where I look (google, YouTube, Reddit, etc.), I either can’t find or I don’t understand the “fat adaptation” part of all of this.

How do I objectively know I’m fat adapted? Meaning, for sure? I’ve read that you “just know”. That seems silly and subjective.

Once fat adapted, does anything change as far as routine? I’ve read that you can ease up on how strict you are with carbs but I’ve heard people say that they’ve been keto or in ketosis for years?

I can probably come up with at least 10 more questions specifically about fat adaptation but I guess we’ll start there.

Background… I started about 2 months ago, I’m fairly active (workout 6 days a week), goal is to only lose about 5-10lbs, currently sitting around 12-13% bf, I am strictly “clean” keto, I test ketones regularly.

Thanks in advance!

(Scott) #14

You can save a lot of grief if you just order without the bun from the get go. This has become natural for me to the point that I can’t imagine consuming a burger with a bun now and not feeling bloated and stuffed. It is also fun asking for extra bacon too. The fries are a mind over matter thing. You can either get them and share with the table (but not eat any) or just say hold the bun and fries. In more of a restaurant setting they will substitute broccoli for the fries if you ask. I was on vacation and felt bad that when the burger came it had the fries that you speak of and I caved, I ate two very small ones.

(Old Baconian) #15

There’s no known way to measure fat-adaptation, so it can only be determined subjectively, but there are a few indicators. First, let me point out that ketosis begins almost immediately after carbohydrate intake drops low enough, because serum glucose and insulin drop, and insulin is the main regulator of ketogenesis (although glucagon plays a role as well, under the right circumstances). The process called fat-adaptation is a cellular adaptation to metabolizing fatty acids in place of glucose and even ketone bodies, thus sparing the glucose and ketones produced by the liver for the organs that require them.

At two months in, you are probably fat-adapted. Part of fat-adaptation involves mitochondrial healing, part the ramping up of the production of some hormone or catalyst, the name of which I forget. Dr. Phinney has a great description of all this on the Virta Health site, if you can find it. I forgot to bookmark it, myself. But these changes take time, which is why fat-adaptation lags behind nutritional ketosis. One useful marker is that people who exercise notice a drop in performance when they embark on a ketogenic diet, and once they reach fat-adaptation, their performance returns to pre-keto levels, and sometimes even exceeds that.

Otherwise, you’re left with a sense of energy and well-being as your primary markers. People occasionally find they need less sleep, so they might find themselves rising before dawn and cleaning the house or working in the yard, for example. Or they might find themselves taking up exercise (shudder!) to have something to do with all that energy.

You can explore how much additional carbohydrate is safe for you to eat above the 20 g/day limit, but we advise waiting till fat-adaptation for that. Where exactly your carb threshold lies is individual and depends on how insulin-resistant you are, for one thing. How advisable exceeding the 20 g/day limit might be in your particular case would depend on whether you are a sugar/carb addict, how well you feel, how much you miss some particular carbohydrate-rich food, and so forth.

(Joe D) #16

I’ve read this a million times… if you’re kicked out of ketosis, you have to “start all over”. I read my ketones with a meter. According to the meter, it’s been reading ketones for a solid 3 weeks. I’m only counting 20-25g carbs today and I did an hour long HIIT session this morning. I say 20-25g because I had a salad at a restaurant today (iceberg lettuce, about an oz of tomato, a little onion, a few Tbsp of ranch dressing, some cheese, and 6oz of grilled chicken. Also had about a 1/2 cup of cottage cheese. It wasn’t anything fancy… pretty boring for a restaurant actually. But I guessed the sizes here. My other meal was prepared in my kitchen and measured to the T. Reading ketones tonight and it reads “Low” which I’ve never seen. I’ve seen it read as low as .1 before. So, low to me means 0? Let’s just say that’s the case…

Hear me out… let’s say I’m 6 weeks in ketosis, no cheats, always reading with a meter, solid. But not fat adapted yet. Then I slip… let’s say I have 60g carbs one day. You mean to tell me that I now have to “start over” and go another 6-8+ weeks to get fat adapted? Those initial 6 weeks are gone from one slip up??

(Ken) #17

No. Read post #11.

(Logan Rezvani) #18

Great Question! Based on my experiences I believe that once your body has learned to efficiently use fat as fuel it will be able to revert back to that state whenever needed rather seamlessly.

My experience with this is as follows:

It took me about 6-8 weeks of being in Ketosis until I felt my body become fat adapted. I stayed in Ketosis for another few weeks after fat adaptation. However, I reverted back to a normal and more balanced diet which included normal amount of carbohydrates. I maintained the normal carb diet (as much as 200 grams a day) for a period of 5 weeks which very obviously took me out of Ketosis. After this five week stretch I decided to get back in to Ketosis and quickly cut the carb intake to around 20 grams a day.

There was a profound difference between getting into Ketosis without being fat adapted (first time) and getting into Ketosis once fat adapted (second time). The first time, I experienced several day long Keot Flu which as you know comes with a severe headache and other painful side effects. This was due to my body struggling and learning to use ketones as an energy source versus glycogen. The second time however, was 100% painless, no keto flu, no head ache and not side effects of any kind whatsoever and I believe this is because my body had previously learned how to use fat for energy and so when the time came it was able to transition from carbs to fat seamlessly.

Good Luck


(Bunny) #19

From the details in your description with the type of lifestyle; weight lifting, cycling, fasting etc. and the time you have been on the ketogenic diet it would take a very long-time for you to be kicked out of being fat adapted irregardless of whether or not your seeing ketones on a meter because you are going into ketosis when you go to sleep at night any way.

When people quit going into ketosis, when they go to sleep at night is when the trouble starts that’s why they need to go on a ketogenic diet?

That carb intake your noting is nothing compared to your lifestyle; your actually oxidizing glucose/sugars or carbohydrates because of your muscle volume so it is highly unlikely it will be stored as fat!

I do not see even a remote possibility of you getting kicked off any kind of wagon in your case because you appear to be in really good (excellent) physical and metabolic shape.

(Scott) #20

Fat adaptation is not a switch that gets flipped on. It is more like a slow gradual slide toward it. Think about it I don’t think I have ever heard someone say “I became fat adapted on ____date.” Therefore the opposite may be true, you don’t go out of or away from adaption like a switch being turned off, you just get a little further away.