Aren't we ALL fat-burners and sugar-burners? What's the difference? page 2

[magicmerl]

The upregulation makes sense, but my understanding is that glucose is used preferentially, meaning that it will be used up entirely before switching over to burning fat. I've never heard of glucose getting saved to be used later while burning fat in the meantime (unless I'm misunderstanding what you meant).

If you correct that when you are in 'surplus' for both glucose and fat, your body will use glucose preferentially. And the modern diet (>300g of glucose a day) is certainly going to put you into glucose burning mode.

But if your glucose intake is low (say ~50g/day) then your body preserves your scarce glucose stores for organs which *have* to run on glucose only, like parts of your brain. It also downshifts your metabolism to run in 'scarcity' mode (which makes it harder to lose weight, since your BEE or base-energy-expenditure goes down), and powers them from fat. This is why VLC people get cold hands and feet (reduced circulation to less essential bodily functions).

[sbhikes]

If you correct that when you are in 'surplus' for both glucose and fat, your body will use glucose preferentially. And the modern diet (>300g of glucose a day) is certainly going to put you into glucose burning mode.

But if your glucose intake is low (say ~50g/day) then your body preserves your scarce glucose stores for organs which *have* to run on glucose only, like parts of your brain. It also downshifts your metabolism to run in 'scarcity' mode (which makes it harder to lose weight, since your BEE or base-energy-expenditure goes down), and powers them from fat. This is why VLC people get cold hands and feet (reduced circulation to less essential bodily functions).

Brain runs on ketones just fine, and only a very small amount of the brain needs glucose, and only as much glucose as your body is fully capable of providing through gluconeogenesis. So only a tiny bit of carbs is useful to your brain and obtaining it from carbohydrates is optional.
Your Brain On Ketones | Psychology Today

[Neckhammer]

If you correct that when you are in 'surplus' for both glucose and fat, your body will use glucose preferentially. And the modern diet (>300g of glucose a day) is certainly going to put you into glucose burning mode.

But if your glucose intake is low (say ~50g/day) then your body preserves your scarce glucose stores for organs which *have* to run on glucose only, like parts of your brain. It also downshifts your metabolism to run in 'scarcity' mode (which makes it harder to lose weight, since your BEE or base-energy-expenditure goes down), and powers them from fat. This is why VLC people get cold hands and feet (reduced circulation to less essential bodily functions).

Magicmerl I usually like your posts but this part "It also downshifts your metabolism to run in 'scarcity' mode (which makes it harder to lose weight, since your BEE or base-energy-expenditure goes down), and powers them from fat." Is fairly much bunk. Fact is that your BEE goes down on any caloric restricted diet. So anytime your attempting to lose weight this will happen.

The real difference is that your body will preferentially burn fats at higher and higher intensities rather than glucose to retain glucose for absolute necessities. That is part of the adaptation of "scarcity" mode...which I find is a positive event considering the much larger supply of fat substrate for energy in the human body.

[Omni]

The upregulation makes sense, but my understanding is that glucose is used preferentially, meaning that it will be used up entirely before switching over to burning fat. I've never heard of glucose getting saved to be used later while burning fat in the meantime (unless I'm misunderstanding what you meant).

Glucose is used preferentialy from the blood, not because it is a prefered fuel, but because it can be damaging if level goes too high.
Our bodies do burn both glucose and fats all the time in various quantities, the question remains as to what the ideal diet ratio is, my feelings are it is somewhere in the range of 3:1 Fats:Carbs, the reasons being we have limited storage capacity for glucose.

Glucose storage in body:
1 - Blood serum, very limited due to the strict control of high/low levels, so not really a storage depot.
2 - Muscle glycogen, +/- 400g, significant but restricted to muscle it is bound in, unavailable to the brain.
3 - Liver glycogen, +/- 120g, primarily reserved to maintain Serum levels and most likely specific for brain functions.
4 - Digestive tract, ???g, this is the only place that can carry a significant quantity of glucose in the form of complex carbs that can be absorbed at a slow enough rate to maintain a fairly constant flow of glucose to maintain serum levels and hence allow one to be a "sugar burner" until digestion is completed, say max 3-4 hours, which goes in with the normal hunger/craving cycles.

Considering any excess glucose/fructose will always be converted to fats by the liver, I doubt you could ever get past 50:50 on a normal 3 meal routine, even if you eliminated all fats from your diet completely. The only possibility would be if you did round the clock snacking to supply a fairly continuous supply of glucose to maintain serum levels on the slightly high side.

Remembering also that solouble fibre and resistant starches will be fermented by gut flora to release Short Chain fatty acids irrespective of whether you are high or low carb, I would say we are all predominantly fat burners, just a question of by how much.

[Daydreamer]

I have a question regarding glucose...etc
While not wanting to be in total ketosis, I'm aiming for the carb curve Mark explains.
I'm typically aiming for somewhere between 70 to 150 (around 100 most days, up to 150 is very unusual) g of carbs.
But as I'm needing a lot of calories, I tend to consume quite a lot of protein along with my fats.
Would it therefore turn my body into a sugar burner ?

[magicmerl]

Brain runs on ketones just fine, and only a very small amount of the brain needs glucose, and only as much glucose as your body is fully capable of providing through gluconeogenesis. So only a tiny bit of carbs is useful to your brain and obtaining it from carbohydrates is optional.
Your Brain On Ketones | Psychology Today

So you're disagreeing that I said part of the brain needs glucose to run by saying that it's only a small part? I understand that the body can synthesise it's own glucose, but what's the point? carbs aren't inherently evil. They are just a macronutrient that is consumed in quite distorted quantities in our current 'fat is evil' food culture.

Magicmerl I usually like your posts but this part "It also downshifts your metabolism to run in 'scarcity' mode (which makes it harder to lose weight, since your BEE or base-energy-expenditure goes down), and powers them from fat." Is fairly much bunk. Fact is that your BEE goes down on any caloric restricted diet. So anytime your attempting to lose weight this will happen.

Fair enough. I could easily be wrong there. From my own personal experiences with IF I got cold hands and feet, and adding banana/kumara/yams back in to my diet made it go away. I had *never* in my life had cold hands before (thinking of it as some sort of female deficiency). My cold hands fix could easily have been because of greater calorific intake, but I certainly noticed that I am very hot at night in bed now on evenings when i have carbs in my meal. And my suspicions were that it was because the extra calories came in the form of carbs, not just because they are extra calories.

I currently have three possible competing theories to explain 'VLC icy fingers'. Either it's an electrolyte imbalance (helped by the potassium in the banana), or it's not enough carbs (helped by the carbs) or it's not enough calories (helped by the carbs....). I guess in some ways this is a little like the 'metabolic advantage'. Maybe it exists, and maybe it doesn't, but if eating a low carb diet works for you, does the mechanism matter that much?

Like, who cares what the freaking cavemen ate? But if mimicing their diet brings someone to eschew frankenfoods, isn't that still a win?

The real difference is that your body will preferentially burn fats at higher and higher intensities rather than glucose to retain glucose for absolute necessities. That is part of the adaptation of "scarcity" mode...which I find is a positive event considering the much larger supply of fat substrate for energy in the human body.

I definitely agree that this is happening.

However, I have noticed that on days when I didn't 'carb load' the night before, I can definitely notice that my hands go cold somewhere between 3pm and 4pm. That's my trigger to break out the bananas for dessert that night

[Omni]

From my own personal experiences with IF I got cold hands and feet, and adding banana/kumara/yams back in to my diet made it go away. I had *never* in my life had cold hands before (thinking of it as some sort of female deficiency). My cold hands fix could easily have been because of greater calorific intake, but I certainly noticed that I am very hot at night in bed now on evenings when i have carbs in my meal. And my suspicions were that it was because the extra calories came in the form of carbs, not just because they are extra calories.

I currently have three possible competing theories to explain 'VLC icy fingers'. Either it's an electrolyte imbalance (helped by the potassium in the banana), or it's not enough carbs (helped by the carbs) or it's not enough calories (helped by the carbs....). I guess in some ways this is a little like the 'metabolic advantage'. Maybe it exists, and maybe it doesn't, but if eating a low carb diet works for you, does the mechanism matter that much?

However, I have noticed that on days when I didn't 'carb load' the night before, I can definitely notice that my hands go cold somewhere between 3pm and 4pm. That's my trigger to break out the bananas for dessert that night

When I switched to Primal it was a health improvement choice, I thought I was pretty much ok, but figured it was a positive move for the longer term, so didn't really expect to see any significant changes in the short term, as I thought I was basically normal/healthy.
But I did have some significant changes and two of them seem to be similar to things you have mentioned.
1 - I did have issues with cold hands/feet, but figured that was genetic as is common in my family, when I switched over the hands/feet improved, the temp was a little better, but, hard to describe, they still get a bit cold, but it doesn't feel uncomfortable like it used to get. The difference between feeling the cold temp, but not feeling cold and I notice this with the rest of my body, my skin surface can get much colder before I get to the shivering. So I can only put this down to better circulation and capilary dilation controls.
2 - I used to get night sweats a few hours after going to bed (also common in family) and these went away when diet changed, after the occasional dietary discretion I would find a bit of a return in the sweats and eventually tracked it back to higher Carb intake, particularly wheat, I put it down to possibly toxins like gluten initially, but now I'm thinking it may well be the additional liver activity in converting excess glucose to triglycerides, the sweats used to last for an hour or two, then my body temp would go down again and I would sleep fine.

I wonder if it is not the glucose liver thing that is creating additional heat in bed for you?

[gopintos]

I am very hot at night in bed now on evenings when i have carbs in my meal. And my suspicions were that it was because the extra calories came in the form of carbs, not just because they are extra calories.

Interesting. I wake up hot and sweaty also. Not profuse, but enough to wake me. Last a few minutes. On and off after about 1am, all night. Usually I can go back to sleep although this past week was not the best for me as far as sleeping. I do take Magnesium and usually a 5g mellatonin. I say "interesting" because I was reading lately to eat carbs in the evening, to sleep BETTER. I was going to try that last week but forgot to pay attention. However ALL my carbs are PM regardless, because I don't do breakfast so about half are in my yogurt/fruit in the afternoon and the other half are with dinner.

This has pretty much happened shortly after going primal and lower carb, although it use to be about 3am. Since it changed to 1am, and semed more frequent, I had blood work done a few weeks ago and I am NOT pre-menie. I was hoping it had to do something with my metabolism working over time. I also heat up after a meal.

[jsa23]

To the original poster: In short, yes - we all *should* be both fat-burners and sugar-burners. I tend to object to the way Mark uses the terms "fat-burner" and "sugar-burner", as the latter is often used almost as a pejorative at times.

If one wants to be scientifically accurate, a more appropriate way to discuss the topic would be in terms of Metabolic Flexibility. Namely, how effectively the body switches between fat-burning and sugar-burning modalities. In general, what Mark and many on these forums refer to as a "fat burner" could more accurately be described as "metabolically flexible".

Mark linked an article from one of his post(warning: pretty dense read) that explains it pretty well here: http://ki.se/content/1/c6/07/80/41/G...20Refrence.pdf

There are other references on can find too, but generally the problem, as I interpret it is the body not fully switching to fat metabolism once glycogen reserves start to fall off, which can lead to other issues such as relying on protein for gluconeogenesis, among other things. Thus, the real discussion should be around "metabolic flexibility" - namely the body's ability to properly transition between fat and carbohydrate as fuel, rather than a strict "fat-burner"/"sugar-burner" dichotomy.

The article that Mark linked my previous reference from is a decent read as well and presents multiple references regarding the benefits of metabolic flexibility, if one looks past the "fat-burner"/"sugar-burner" terminology:
What Does it Mean to Be Fat-Adapted? | Mark's Daily Apple

In my opinion, the above post is probably one of the most useful, informative posts that's been posted on this site, if one reads through(and understands) all the information in the links the article references.

[BestBetter]

To the original poster: In short, yes - we all *should* be both fat-burners and sugar-burners. I tend to object to the way Mark uses the terms "fat-burner" and "sugar-burner", as the latter is often used almost as a pejorative at times.

If one wants to be scientifically accurate, a more appropriate way to discuss the topic would be in terms of Metabolic Flexibility. Namely, how effectively the body switches between fat-burning and sugar-burning modalities. In general, what Mark and many on these forums refer to as a "fat burner" could more accurately be described as "metabolically flexible".

Mark linked an article from one of his post(warning: pretty dense read) that explains it pretty well here: http://ki.se/content/1/c6/07/80/41/G...20Refrence.pdf

There are other references on can find too, but generally the problem, as I interpret it is the body not fully switching to fat metabolism once glycogen reserves start to fall off, which can lead to other issues such as relying on protein for gluconeogenesis, among other things. Thus, the real discussion should be around "metabolic flexibility" - namely the body's ability to properly transition between fat and carbohydrate as fuel, rather than a strict "fat-burner"/"sugar-burner" dichotomy.

The article that Mark linked my previous reference from is a decent read as well and presents multiple references regarding the benefits of metabolic flexibility, if one looks past the "fat-burner"/"sugar-burner" terminology:
What Does it Mean to Be Fat-Adapted? | Mark's Daily Apple

In my opinion, the above post is probably one of the most useful, informative posts that's been posted on this site, if one reads through(and understands) all the information in the links the article references.

Jsa,

I re-read the above article you linked. Somewhere in the middle of it, Mark writes that, "A fat-burning beast can effectively burn stored fat for energy throughout the day. If you can handle missing meals and are able to go hours without getting ravenous and cranky (or craving carbs), you’re likely fat-adapted."

Since I've dramatically increased my carbs/sugars and lowered my fat intake, I have not become excessively hungry or cranky, and it is still just as easy for me to skip a meal. I'm assuming that likely my lowered hunger levels are due to the heat of summer, but even still, I've been surprised by how easy it is to not be obsessed with food all the time. By Mark's own words, this should theoretically mean that I'm 'fat-adapted', even though I'm eating low-fat/high carb right now.

I think that 'metabolic flexibility' is probably a much more accurate way of discussing this, and I'm wondering how long metabolic flexibility lasts. For example, maybe I'm experiencing a 'honeymoon phase' right now that will change, but if so, what is the cause of that change, and what would be the biological explanation for the honeymoon phase?