Maybe someone can post a link or an answer to this question which I was thinking about the other day. Sorry if this has already been asked.

I was at the gym thinking about how exercise burns fat (I actually don't really know exactly how it works - exactly.)

Question is: Is the body's fat burning process the same in exercise as it is in ketosis?

It seems to me like the body would have to go through the same steps to burn fat whether it's through exercise or ketosis (whatever exactly that process is.)

The way I understand it is when a person exercises, stores of glucose and fat are being burned for fuel.

If exercise and ketosis are handled the same, wouldn't that automatically make the Atkins diet good for you?

Any thoughts?

I hope you get a lot of responses to this. Its a good question. Recently I bought a scale that measures body weight and body fat. I have been weighing every morning and my weight is going down, but the fat percentage was going up until I started being more active. I still have a long way to go. I don't want to stay at 30% body fat.

Mary,

Where ever did you get that kind of scale. Does it take a rocket scientist to work? I need simple. Debby

I can't wait to see some of the answers you get from the truly informed people around here. But until then, I'l share my personal experiences:

I'm a vegetarian low carber, and when I first went low carb, I noticed a lot of people complaining that they couldn't get into ketosis. Hmmmm. If it should be difficult for anybody, it should be difficult for a veggie, right? Anyway...

I also did a lot of exercise videos. Sometime really tough ones, too. And you know what-- [B]I NEVER[B] had any trouble getting into ketosis. (Oh happy, happy, joy, joy! Faith is dancing.) I lost 21 lbs with that combination last summer, too. In fact, I think if you exercise, you can probably eat a few more carbs than the next guy. (But YMMV.)

So, I may not have any scientific answers to your question. But I do have my own personal experience that suggest low carbing and exercise make a winning combination.

Faith

I'd ignore anything fodus posts. Every one of their other posts has been anti LC.

I'll reply because it seems like the question is interesting to some...
The short answer is no, they are not the same.
Ketosis occurs when there is incomplete oxidation of fatty acids. As long as enough carbohydrate is available, fats will be burned completely.

Excerise uses energy at a higher rate than when you are just sitting around but it does not produces energy in a fundamentaly different way.

If you are already in a fat-burning state, you will most likely burn a higher percentage of fat during the workout. But it depends somewhat on the type of work also. Anaerobic, high intensity will use ATP/CP pathways first, then glycogen, then fat.
Just sitting around you're burning mostly fat. Low intesity your buring mostly fat.
This does not mean that low intensity is better for buring fat however. You may burn more calories during high intensity training, both during and after the activity, and therefore end up with more of a calorie deficit and thus more fat buring over the course of the day.

Ketosis is mostly a function of lack of carbohydrate not induced by training. The exception is that if you do a workout that depletes glycogen you will then have less carbohydrate in your body and may go into ketosis faster than if you had not worked out.

Now I'm confused again. I posted a question on a recent 'metabolic advantage of low carb' thread about whether there was a difference between ketosis (exercise or dietarily induced) and burning FFA's in your mitochondria without a ketone in sight. Somebody replied with quotes from some biochem texts which stated quite clearly that FFA metabolism directly in your mitochondria is a quite distinct metabolic energy pathway to ketosis. They both end up using acetyl CoA in cells, but get there via different metabolic pathways. Ketosis is very inefficient, which makes it such a star turn for weightloss, whereas free fatty acid burning in mitochondria is a very clean burn. Particularly because direct FFA metabolism in cells does not produce lactate as a by product as glycogen does. Both metabolize fat of course, just differently. So can you be burning just fat for energy, no glycogen, and not be in ketosis at all, particularly when you low carb long term? MPS and Built, HELP!

I found some good info on Exercise Intensity and Fuel use, but alas, this is not what my orginal question was about.

Exercise Intensity and Fuel Use
The relative contributions of fat and carbohydrate to energy vary with exercise intensity. Low-intensity activities such as walking strongly stimulate lipolysis from peripheral adipocytes, while intramuscular triglycerides contribute little or nothing to total energy expenditure (1). The rate of carbohydrate use is also low: carbohydrate needs are met predominantly by circulating blood glucose, with little or no muscle glycogen breakdown (figure 1: not shown). The rate of appearance of fatty acids into the plasma peaks during low-intensity exercise (25% to 30% of VO2 max) and then declines as exercise intensity increases.

In contrast, the rate of fat oxidation is highest during moderate activity such as easy jogging (65% of VO2 max). At such an intensity, plasma free fatty acids and intramuscular triglyceride contribute equally to the overall rate of fat oxidation. During high-intensity exercise (85% of VO2 max), the rate of total fat oxidation falls, mainly because the appearance of fatty acids into the plasma is suppressed. At the same time, lipolysis of intramuscular triglycerides does not rise substantially when exercise intensity increases from 65% to 85% of VO2 max. This would not affect recreational athletes because most cannot sustain high-intensity exercise for more than 10 to 15 minutes without accumulating high (greater than 10 mM) concentrations of lactic acid in the working muscles and blood, which would cause discomfort and stop activity.

When low-intensity exercise continues more than 90 minutes, the pattern of substrate metabolism changes little relative to the first 20 to 30 minutes of exercise. The same is true of moderate-intensity exercise (65% of VO2 max): the rate of total fat or carbohydrate oxidation changes little after 2 hours of jogging or cycling at this intensity compared with the first 30 minutes. However, this level of exercise induces a progressive increase in the mobilization of fatty acids from peripheral adipocytes into the plasma (1). Therefore, the contribution of intramuscular substrates (triglyceride and glycogen) to total energy expenditure probably decreases when the duration of moderate-intensity exercise increases beyond 90 minutes.

Your body will adapt over time to be able to use FFA instead of ketones. So less ketones are needed/produced as time goes by.
Your body can use protein to produce glucose and even glycogen to some extent.
Just because your don't show ketones on the urine strip doens't mean you're not in ketosis. It just means that you don't have many excess ketones that your body is being forced to dispose of. (This may(??) negate this aspect of the metabolic advantage over time. You would still have the high cost of converting protein to glucose though)

Well, now THAT was some interesting information!
Thanks for you reply!

And your last paragraph explains why as a veggie during induction, I was always able to get into ketosis if I exercised. (For veggies, going to 20 grams of carbs a day is a LOT harder. I can get down to 30-40 grams of carbs okay though. But I do wonder-- if I could get into ketosis as a veggie, why do some meat eaters have a hard time going there? It would seem that doing induction would be easier for them, considering the wider range of foods they have available to them??? Oh well. That's probably another subject.)

Faith

WOW!

As always mps, an excellent and informative post.

I'm pretty certain I did post a few negative comments on this board over a YEAR ago. I've been on the Atkins/S. Beach for about 7 months and I'm feeling great! Please don't hold a grudge against someone who didn't really understand the complexity of the diet and asked a few questions.

I think my question of exercise and ketosis is very difficult to explain.

1. When I exercise I'm burning different types of fuel. Stored glucose and FAT are two such fuels (I think).

2. When I'm following Atkins my body is also burning FAT for fuel. Ketosis.

OK: My question is: Does the body break down, process, etc, FAT fuel differently in these two cases or is the FAT fuel all the same to the body?

Does the body say: "Hey, we've got some FAT for fuel, a FAT is a FAT, is a FAT. Let's get to work." Or does it say, "Hey this is exercise FAT and it's way different than Ketosis FAT."

Does that make sense?

I think the confusion here is about ketosis and fat burning. If you are in ketosis then you are burning fat incompletely and producing ketones. If your not in ketosis that does not mean that you are not burning fat. It's all the same fat... just used completely in the Krebs cycle (fat burning/ATP/energy producing pathway) or not. Your workout will have no effect on this. It will just speed up whichever fat burning process you are in.

Your question is difficult to answer without me knowing what you know about the causes of ketosis and fat metabolism. But anyway, as far as fat burning... it's all the same fat and the same process, workout or not. The workout will just make it happen at a faster rate because you need the energy at that time.

I hope this helps...?

MPS this has been REALLY REALLY helpful! I guess the long and short of it is that FAT is FAT to the body but Ketosis generates the Ketone by-product and exercise does not.

So one could say that exercise produces a more clean-burning FAT??

Thanks for all the patience and help.

This seems like a pretty good article on Fat Burning During Exercise. Even gets into a paragraph or two talking about High-fat diets and exercise.

http://www.physsportsmed.com/issues...9sep/hawley.htm

thanks again!!!!