Fat burning vs carb use page

[Owen]

Hi all,

I've been on Paleo for four weeks. In your experience is it true that you become a more efficient fat burner and over time you are less reliant on carbs, or do you always need carbs if you are exercising for any extended period of time? At the moment I can walk for maybe 1.5 hours in a day on a low/no carb diet, but if I go over this, I am totally zonked out by the time I get home.

Also, if you have achieved a fat burning metabolism, what is this like? Does it give you more stamina than you had before?

[runningout]

Hi all,

I've been on Paleo for four weeks. In your experience is it true that you become a more efficient fat burner and over time you are less reliant on carbs, or do you always need carbs if you are exercising for any extended period of time? At the moment I can walk for maybe 1.5 hours in a day on a low/no carb diet, but if I go over this, I am totally zonked out by the time I get home.

Also, if you have achieved a fat burning metabolism, what is this like? Does it give you more stamina than you had before?

Yes, certainly you could get better fat burner up to (almost) no reliance on carbs at all on easy-modest exersices. Eventually you could walk all day without carb refills before or during.
How good fat burner one is, depends much on training and dietary history and genetics. You can find studies on fat burning improvements, with avoiding carbs (inlc. sports drinks and fruits&juices) just before and during and exersices on low enough intensity. One can boost the percentage of fat as fuel and the heart rate/intencity where fat can be burned. But eventually If you want to race on 10k, you'd be burning sugar heavily anyway.

Doing everything right, should make noticeable change in 6-8 weeks. Brisk long walks before breakfast/meal are good way to go. Walking & running are better than cycling based on some studies (maybe because humans have cycled just short time but walked quite a long time, so there probably has been some evolution..)
Maybe the biggest change is that you can skip the meal without noticing it, and you'll get over the bonks soon.

In some scientific papers they talk about improvement in RER (Respitory Exchange Ratio), which varies from 0.7 (100% fat oxidation) to1.0 (100% sugar burn)

story (& nice curves) on training intensity: Dr. Deyo | Active Metabolic Test | Metabolic Testing | Slow Metabolism | Fast Metabolism Newport Beach | Active Metabolic Rate | Jason Deyo | Resting Metabolism | Nutrition By Dr. Deyo | Newport Beach | :: Dr. Deyo ::

[kot]

story (& nice curves) on training intensity: Dr. Deyo | Active Metabolic Test | Metabolic Testing | Slow Metabolism | Fast Metabolism Newport Beach | Active Metabolic Rate | Jason Deyo | Resting Metabolism | Nutrition By Dr. Deyo | Newport Beach | :: Dr. Deyo ::

Your link is an excellent graphic representation of what runners call "base training". And it works! It trains your mitochondria to work more efficiently. This is the “Move frequently at a slow pace” principal. After diet it is the next step to becoming a “fat burning beast”.

Here is a little background Freedom's Run Training Guide. and Train Smart This Winter: Base Training Basics | Active.com

A basic how to do it Articles

[Gorbag]

As said before; The body IS a very efficient fat-burner, since fat is used with low intensity activities by everybody, like walking or sitting still, and glucose/glycogen is used by the brain and also with higher intensity muscle work. Most of the time the body uses both fuels at the same time. The question is not whether the body can become a more efficient fatburner or not, but whether it can be better to make glucose from amino acids! High intensity activities need glucose for fuel and this must come from carbs or protein. So becoming "a fatburning beast" is bullshit on stilts, since it doesn’t work through those pathways, but you may become "a proteinburning beast", instead, i.e. more adapted to gluconeogenesis. Well, actually a proteinburning beast is an exaggeration because it will still be less efficient than ingesting carbs for high intensity endurance work, but it may be more than enough for normal everyday activities…

[Neckhammer]

As said before; The body IS a very efficient fat-burner, since fat is used with low intensity activities by everybody, like walking or sitting still, and glucose/glycogen is used by the brain and also with higher intensity muscle work. Most of the time the body uses both fuels at the same time. The question is not whether the body can become a more efficient fatburner or not, but whether it can be better to make glucose from amino acids! High intensity activities need glucose for fuel and this must come from carbs or protein. So becoming "a fatburning beast" is bullshit on stilts, since it doesn’t work through those pathways, but you may become "a proteinburning beast", instead, i.e. more adapted to gluconeogenesis. Well, actually a proteinburning beast is an exaggeration because it will still be less efficient than ingesting carbs for high intensity endurance work, but it may be more than enough for normal everyday activities…

I disagree. It really actually is about becoming a better fat burner. For instance, you really do lose access to your fat stores as a source of energy when your insulin is raised. If your suffering from insulin resistance then you likely also have hyperinsulinemia and have little access to your fat stores. That is the real reason you have crashes and are riding a sugar roller coaster. Fat would provide you with steady energy if you could access it.

So I'm talking about metabolic syndrome right? Well then I'm talking about 60+% of Americans. Your obviously not one of them, but you are actually in the minority!

Furthermore, not only are we talking about burning fat but in the end we are talking about a training method that allows you to burn fat at higher levels of intensity. You can train low and slow to build up your aerobic capacity (not cardio fake aerobics...the real metabolic kind). For instance you may start off having to keep your heart rate under 125 bpm to stay in a fat burning zone (above which you start to rely on glucose), but if you continue to train in that zone and rely on fats you can increase that number and intensity. Burning fat up at 135, 140 or more bpm at increasing intensities.

Given that at any time you have hundreds of thousands up to a MILLION calories of fat available for energy....seems like having access to that at higher intensities would provide a significant edge. I mean you only have about 2000 calories of glucose available...only about 100g of which are there for the brain at any given time.

[Gorbag]

I disagree. It really actually is about becoming a better fat burner. For instance, you really do lose access to your fat stores as a source of energy when your insulin is raised. If your suffering from insulin resistance then you likely also have hyperinsulinemia and have little access to your fat stores. That is the real reason you have crashes and are riding a sugar roller coaster. Fat would provide you with steady energy if you could access it.

You cannot burn much stored bodyfat when insulin is high, but the body will still burn fat every minute of the day and the night too! Insulin will lower fat oxidation somehow but it is not a switch-off button, so maybe around 35% less fat oxidation when insulin levels are high. The real problem that the body meet when not ingesting carbohydrates is not to be a better fat burner, since this is a job the body can handle very well, but to get enough glucose from somewhere! So, even with ketone bodies are present for some fuel, the body must also get enough glucose, and this it must get from amino acids! Also, the sugar rollercoaster as I know very well, doesen't mean that the body stop burning fat when high on insulin.

So I'm talking about metabolic syndrome right? Well then I'm talking about 60+% of Americans. Your obviously not one of them, but you are actually in the minority!

The so called metabolic syndrome is only another word for being fat! And yes, it changes the way your hormones functions, make you insulin resistant etc. When the body have too much body fat it even changes the way a person feel and think, due to hormones.

Furthermore, not only are we talking about burning fat but in the end we are talking about a training method that allows you to burn fat at higher levels of intensity. You can train low and slow to build up your aerobic capacity (not cardio fake aerobics...the real metabolic kind). For instance you may start off having to keep your heart rate under 125 bpm to stay in a fat burning zone (above which you start to rely on glucose), but if you continue to train in that zone and rely on fats you can increase that number and intensity. Burning fat up at 135, 140 or more bpm at increasing intensities. Given that at any time you have hundreds of thousands up to a MILLION calories of fat available for energy....seems like having access to that at higher intensities would provide a significant edge. I mean you only have about 2000 calories of glucose available...only about 100g of which are there for the brain at any given time.

This is a misunderstanding of how the body works in my opinion. When the intensity goes up the body need more glucose to cover the high intensity work, and it will take it from protein if not having enough glucose/glycogen. That's also the reason why marathon runners have such atrophied muscles, because they get more efficient in digging into lean bodymass when in need of glucose, so they adapt in becoming a protein burning beast...

Some references:

Busting the Great Myths of Fat Burning - For Dummies

Fat Burning: using body fat instead of carbohydrates as fuel

[Neckhammer]

You cannot burn much stored bodyfat when insulin is high, but the body will still burn fat every minute of the day and the night too! Insulin will lower fat oxidation somehow but it is not a switch-off button, so maybe around 35% less fat oxidation when insulin levels are high. The real problem that the body meet when not ingesting carbohydrates is not to be a better fat burner, since this is a job the body can handle very well, but to get enough glucose from somewhere! So, even with ketone bodies are present for some fuel, the body must also get enough glucose, and this it must get from amino acids! Also, the sugar rollercoaster as I know very well, doesen't mean that the body stop burning fat when high on insulin.



The so called metabolic syndrome is only another word for being fat! And yes, it changes the way your hormones functions, make you insulin resistant etc. When the body have too much body fat it even changes the way a person feel and think, due to hormones.



This is a misunderstanding of how the body works in my opinion. When the intensity goes up the body need more glucose to cover the high intensity work, and it will take it from protein if not having enough glucose/glycogen. That's also the reason why marathon runners have such atrophied muscles, because they get more efficient in digging into lean bodymass when in need of glucose, so they adapt in becoming a protein burning beast...

Some references:

Busting the Great Myths of Fat Burning - For Dummies

Fat Burning: using body fat instead of carbohydrates as fuel

As to insulin I was talking about the access to fat stores. You effectively do shut off lypolisis when insulin levels are raised. So at a level it actually is quite like a switch. So in someone with perpetually raised levels you can see why this could be problematic. Even if we are just talking 35-50% difference or some such vs. a person with a normal (call it flexible rather than fat burning if you like) metabolism.

Also I would not look at gluconeogenisis as being an activity dependant entity. Its more of a constant process that stores up fuel for later. If you perform high intensity work you burn glycogen. But you don't ramp up gluconeogenisis right then and there to produce that glycogen. Its more of a steady state that will refill your glycogen stores while you rest so that it's available next time you perform that sort of work. You are limited to how much of this can occur (think 200g/day or so), so if you plan to exercise at high intensities very frequently best eat some starch.

I don't think what was written about raising your ability to oxidize fat at higher levels is a misunderstanding at all. Its actually a quantifiable result.


And there are a lot of issues with marathon runners but I don't think its digging into muscles for glucose......at all. Its that they are in a very specializes sport that selects for that body type. Endurance musculature is selected for over hypertrophy and strength as these latter add mass, but are not needed to run long distances...just slowing you down. Has nothing to do with gluconeogenisis eating up their muscle mass.

[Gorbag]

As to insulin I was talking about the access to fat stores. You effectively do shut off lypolisis when insulin levels are raised. So at a level it actually is quite like a switch. So in someone with perpetually raised levels you can see why this could be problematic. Even if we are just talking 35-50% difference or some such vs. a person with a normal (call it flexible rather than fat burning if you like) metabolism.

High insulin is less of a problem for the obese than being in a energy surplus or at maintenance in my opinion. Fat people are good fat burners, and can rely on fat for energy far better than a person low on bodyfat. The problem as I see it is the energy balance and not insulin per se...

Also I would not look at gluconeogenisis as being an activity dependant entity. Its more of a constant process that stores up fuel for later. If you perform high intensity work you burn glycogen. But you don't ramp up gluconeogenisis right then and there to produce that glycogen. Its more of a steady state that will refill your glycogen stores while you rest so that it's available next time you perform that sort of work. You are limited to how much of this can occur (think 200g/day or so), so if you plan to exercise at high intensities very frequently best eat some starch.

Glucoseneogenesis is a steady state activity yes, but the body will ramp it up when getting catabolic and desperate for glucose.

I don't think what was written about raising your ability to oxidize fat at higher levels is a misunderstanding at all. Its actually a quantifiable result.

It's a misunderstanding because people are confusing maximal ability of oxidizing fat with relative ability. Fat is the preferred fuel of the body when doing low intensity work or resting.

And there are a lot of issues with marathon runners but I don't think its digging into muscles for glucose......at all. Its that they are in a very specializes sport that selects for that body type. Endurance musculature is selected for over hypertrophy and strength as these latter add mass, but are not needed to run long distances...just slowing you down. Has nothing to do with gluconeogenisis eating up their muscle mass.

Yes it has, long distance running is extremely catabolic, and there will be a deficit of sufficient free fatty acids and glucose in the blood, so the body must get energy from somewhere and it takes it from proteins...

[jakey]

i see a lot of confusion about insulin levels and carb eating based on a failure to distinguish between fasting hyperinsulinemia (a pathological condition), and post-prandial insulin spikes, which are utterly normal. neckhammer, i don't know if you fall into this category, but there are lots of smart people that seem to confuse this, and argue for eating no carbs because the insulin spike after the meal will blunt lypolisis. that's ridiculous. if you're insulin levels are chronically elevated, without regard to meal timing, you have a major problem, and are pre-diabetic. otherwise, there's no problem with an insulin spike, and any normal body can burn both carbs and fat, and should be able to switch with ease. if you eat more fat, you'll burn more fat, eat more carbs, burn more carbs.

[Neckhammer]

i see a lot of confusion about insulin levels and carb eating based on a failure to distinguish between fasting hyperinsulinemia (a pathological condition), and post-prandial insulin spikes, which are utterly normal. neckhammer, i don't know if you fall into this category, but there are lots of smart people that seem to confuse this, and argue for eating no carbs because the insulin spike after the meal will blunt lypolisis. that's ridiculous. if you're insulin levels are chronically elevated, without regard to meal timing, you have a major problem, and are pre-diabetic. otherwise, there's no problem with an insulin spike, and any normal body can burn both carbs and fat, and should be able to switch with ease. if you eat more fat, you'll burn more fat, eat more carbs, burn more carbs.

Nah, I get the difference...which was why I was saying that in a sense the whole "fat burner" bit is pointedly aimed at those who have metabolic syndrome. I.e. a pathological condition. It's a common problem in the US which is why I said that someone fit, such as Gorbag, is correct in his assertions relating to a normal metabolism burning both and being flexible. I mean heck even Mark's definition is something along the lines of "if you can go a few hours or skip breakfast without crashing your a fat burner".

I'm actually not arguing against eating carbs. But, I do think there is something to be said for hitting that Goldilocks level where your eating just enough. I also think there is something to be said for working on raising your particular ability to burn fat for fuel at higher intensities via working in the right HR zone. I'm experimenting with that on myself right now though, so I guess I'll see.