Fat Adapted: is it real?

#1

We talk about being fat adapted all the time in here, and I get the concept, but I’m wondering if there is science out there on the topic. It seems like anecdotal evidence is present for a shift after being low carb for a time, but is there really a mechanism in the body that changes? What is the biochemistry behind the body deciding to prefer burning fat?

(bulkbiker) #2

When you take in very little glucose and have exhausted your stores what else does the body have to run on?

#3

Yes, it burns fat but why the “six to eight weeks to become fat adapted” mantra we read about so much in various forums (including here)?

(bulkbiker) #4

Cos thats when you have got through your glucose stores completely and that also explains why it takes some more time than others…

(Bacon is a many-splendoured thing) #5

https://blog.virtahealth.com/keto-adapted/

#6

It takes eight weeks to burn through glucose stores??

#7

Thanks for this! I am going to bookmark it for later. I skimmed it and it seems like there is still a lot of research that needs to be done on what’s actually happening as the body gets used to the lower carb input.

(bulkbiker) #8

Depends how much you have …as an ex T2 diabetic I must have had a shit ton stored everywhere… nerves blood vessels you name it… for someone with more regular metabolism then it could be quicker… also of course if you “cheat” halfway through you could be restocking those stores… there are loads of reasons why it takes time…

(Cindy) #9

Interesting! It’s written, I think, from more of an exercise stance, which I don’t have trouble with lately since I’m not doing any “formal” exercise. LOL! I like that they use the term “keto-adaptation” vs fat-adapted.

In other words, the process of keto-adaptation that allows for normal or increased exercise performance lags well behind the level of ketones in the blood.

This is where they’re differentiating between just ketone production and keto-adaptation. Also interesting that they find that highly trained runners, after 6 months, store the same amount of glycogen in their muscles as carb burners.

I think it all just shows that human beings have highly adaptive systems. A vegetarian will lose some of the enzymes to digest meat, which makes sense, because making an enzyme that isn’t needed is very inefficient and a waste of resources. Start eating meat again, and those enzymes return/increase. The same (I believe) is true of a high carb diet in that the mechanisms for using fat for energy are reduced in the presence of so much sugar. Instead, your body has to be in a fat storage mode so that glucose in the bloodstream is reduced.

Severely limit carbs and then, just like the vegetarian turned meat-eater, your body recognizes the need for more fat burning enzymes and the need to use ketones for energy. Because I’m not a runner or other highly trained athlete, I’d say that it’s at that point that a person is “fat-adapted.” NOT necessarily keto-adapted though in the context of that article.

That’s why (again, just my personal take on all this), after your biochemistry has been pushed toward fat/ketones as an energy source, having an occasional day of too many carbs doesn’t cause a complete reversal of fat-adaptation because it’s just a “blip”…all the fat burning machinery is still there. Now, eat high carbs for several days or weeks and it’s all going to reverse again.

(Scott) #10

I could not in any real way define when I was fat adapted. I could taste the start of ketosis. The only way I could assume that I was fat adapted is my running energy was so low I had to walk at times which is not typical for me. Then suddenly at about the three month mark I was running and thought “I have my energy back”, that was it for me.

(Robert C) #11

I thought one of the major differences between just being in ketosis vs. being fat-adapted was that, once fat adapted, the body can switch between the two fuel sources easily (to great benefit for athletic performance if that is what is desired).

Just a week into the Keto diet and have a 200 gram carb day and you probably get to redo some Keto flu. Maybe several days to a week of strict Keto before your blood ketone numbers recover?

But, after months of strict Keto (i.e. once truly fat-adapted) that same 200 gram carb day will be handled much differently. Vacuum up and burn the carbs, not cause some “insulin resistance” effects, and then easily switch right back to producing and burning Ketones.

Probably depends a lot on the person’s original insulin issues.

Not sure this is all correct but, it seems to me that, if you have been Keto for just a week or two, you have to actually fast to get back to good numbers quickly vs. being fat-adapted, just having to avoid carbs to get back to good numbers quickly.

(John) #12

I don’t know the science behind it all. Something to do with mitochondria in the cells being created, from some article I read a while back. Sounded reasonable.

From experience, what I can tell you is that during the transition from a carb-burning metabolism to a fat-burning metabolism, I felt worse for the most part, with ups and downs in fatigue and energy levels, gradually but choppily improving, for about the first 8 weeks. By 12 weeks, I felt perfectly normal with steady energy levels and no ups and downs.

Starting in about week 4 was when I had the beginnings of significant appetite control and could skip meals and go all day without needing to have snacks on hand. By week 12 I could easily do 24 hour fasts without even thinking about it.

Now, in week 27 or so, I can eat, not eat, have some carbs, have no carbs, it doesn’t seem to matter. I can go 48 hours without eating without much effort and it doesn’t affect my fatigue or energy levels at all, because my body is easily able to access my remaining fat stores. That was not the case when I started, even though I had twice as much fat stores available.

So that’s what being “fat adapted” is for me - it is a long process, with steady but uneven progress. 6 to 12 weeks is where it really seems to start kicking in, with continuing improvement past that.

As far as glycogen stores being depleted - that should happen within the first few days / first week of a very low carb intake. That’s not fat adaptation. That’s just glycogen depletion. Your body is forced to use fat for energy because it doesn’t have much else to use. It’s just not very good at it yet. Hence the famous “keto flu” symptoms some people experience.

#13

This is my first thought too, as to the biochemistry behind becoming “fat adapted.” Also possibly the amount of fat stored in your liver, which the liver is converting into glucose? Some people run low on that easy fuel source for the liver faster…?

#14

Something, something, mitochondria. lol! I can see that!

#15

But I’m thinking that the enzymes we are talking about for vegetarians are located in the digestive system, whereas the fat-burning mechanism is in the fat cells of the body, presumably, and not in the digestive system. So we’re not really talking about enzymes but about some other signaling that the body is using to tell itself to burn more fat and stop waiting around for more glucose.

(Windmill Tilter) #16

Here is some compelling science on fat adaptation. This journal article explores the differences in fat burning between elite Iron Man competitors and ultra endurance athletes who eat diets that are either carbohydrate based or ketogenic. The keto athletes have some truly bad ass mitochondria. Talk about fat adapted!!!:yum:

#17

Lets clear one thing up real quick: it does not take weeks to get rid of the glucose stores in the body.

You get rid of your glycogen (the closest to long term stores of glucose) within a day (16 hours is the usual thought, but may vary on some factors).

You actually will continue to have glucose in your body 20 years later even on zero carb though, because your body will produce it through gluconeogenesis to provide it to what needs it (parts of the brain, possibly some other organs), but that’s done in amounts that don’t typically conflict with ketosis (otherwise we’d never get into ketosis).

As for other scientific research on the matter, Drs. Phinney and Volek have done a lot of the major research on the matter, and in the blog PaulL linked you may notice many of the citations are to their work or projects they were involved in (not all, others have worked in the field as well). You should be able to find some of their published papers on the matter around. A lot of their stuff was done monitoring athletes, particularly endurance athletes, but there’s more out there as well on this topic if I recall.

The major difference after complete adaptation is usually focused on performance. Athletes will notice they are unable to achieve quite what they did before for a while (speed, weight lifts, etc) for a while during adaptation, but by the end frequently they’ll do better than before the switch. I believe there are other factors measured though (amount of oxygen used, heart rates, other measurements of energy expenditure over time, etc). Essentially, it’s when the body is used to it enough to fully utilize fats and has retrained itself to use them to peak (or high level) performance.

(Rob Grantham) #18

Isn’t part of the process of adaptation actually that your body is better at deriving glucose from protein? I for one feel much better when eating more protein

(Doug) #19

John :+1:

Agree - glycogen depletion is one thing, and the body getting used to using the metabolic pathways for burning fat, making ketones, etc., is another.

I think this is a third thing. Long-term adaptation to a ketogenic diet does increase the number of mitochondria, at least in rats, as well as making each mitochondrion function better. This may offset some of the built-in advantage that carbohydrates have as a fuel source, i.e. they come with oxygen atoms already. It also would explain how athletes can do very well after getting truly fat-adpated.

Keto also increases the amount of phosphocreatine - one of the most basic and fast-acting energy sources we have. It goes to the production of ATP - the energy-supplier that keeps organisms alive, the real “currency of life.”. We don’t have much ATP - somewhere around 200 or 250 grams, but we use a LOT of it - roughly our own body weight, per day, or even more with long strenuous exercise. So an enormous amount of recycling is done.

For energy, a phosphate group is split off the ATP molecule, turning it into ADP. Phosphocreatine steps in and converts ADP back to ATP by giving back a phosphate group.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1867088/

#20

I don’t recall hearing that benefit in particular, but I have heard the various processes used (or hormones involved in the process) in ketosis get up regulated over time and use, and gluconeogenesis is one such process. So, yea, perhaps that gets better, though the more usually focused on aspect is better ability to utilize and produce ketones from fat.