Active Low-Carber Forums - Metabolic Edge For Low Carbohydrate Diets: All Calories Are NOT Alike

Active Low-Carber Forums (http://forum.lowcarber.org/index.php)

- LC Research/Media (http://forum.lowcarber.org/forumdisplay.php?f=4)

- - Metabolic Edge For Low Carbohydrate Diets: All Calories Are NOT Alike (http://forum.lowcarber.org/showthread.php?t=201074)

Quote:

Originally Posted by cc48510

I did some searching, and it appears that once various fuels are actually metabolized, the percentage of available released is similar for both Fat and Carbs (about half.) But, the real issue is not what percentage is released, but what is wasted and how the energy is used. A "High Protein/Low Carb" diet is believed to be less efficient by some because it releases more energy as heat than a High Carb Diet. One other theory is that when ketone levels begin to rise too high, the body has to excrete them to keep its pH within an acceptable range. Thus, the body excretes fuels (Ketones) unused.

Unless you're a Diabetic, you don't excrete Glucose unused. Glucose is very efficient in that manner. If its not used its either converted back to Glucose/Glycogen, or converted to Fat, and stored on the body. Even in an Anaerobic Metabolism, when Glucose yields very little ATP (Energy) per unit of Glucose, it produces a byproduct (Lactate,) which the body can further Metabolized to get more ATP (Energy.) Lactate can also be converted back to Glucose [with very little loss of Energy] later on, and used again.

http://web.indstate.edu/thcme/mwkin...metabolism.html

Protein is unique in that depending on the Amino Acid composition, it may be metabolized more like Carbs or more like Fat. Amino Acids come in 3 types: Ketogenic, Glucogenic, and Keto/Glucogenic. In some instances, Amino Acids can be directly metabolized for energy.

The Ketogenic Amino Acids (Lysine and Leucine) CANNOT be converted the Glucose. They are metabolized to Acetyl CoA, the same stuff Fatty Acids are Metabolized to. From there, they are metabolized the same as Fatty Acids, including the possibility of being converted to Ketone Bodies.

The Keto/Glucogenic Amino Acids (Isoleucine, Phenylalanine, Threonine, Tryptophan, and Tyrosine) can be metabolized to either Acetyl CoA, Pyruvate, TCA Intermediates, or a combination thereof. Pyruvate and TCA Intermediates can be either metabolized for energy or converted to Glucose via Glucogenesis.

The Glucogenic Amino Acids (Glutamate, Aspartate, Alanine, Ornithine, Proline, Serine, Cysteine, Methionine, and Glycine) CANNOT be directly metabolized to Acetyl CoA, and thus don't yield Ketone Bodies. They are metabolized to Pyruvate or TCA Intermediates, which may be metabolized for energy or converted to Glucose.

Fascinating! But I'm still not really clear wether using fatty acids directly in the mitochondria as acetyl Co A is a separate process and energy pathway to ketosis. That is, can you be using FFA's directly in the mitochondria of most cells for energy without a ketone in sight or are ketones a necessary part of energy production from fat. Note that I'm not talking about the mobilization of body fat stores by glucagon into FFA's which can then be available for energy. So the FFA's can be either dietary or bodyfat (or both ;) ), but are ketones a necessary part of them being utilized for energy, or just one such way. I've never had bodyweight issues, and I've never been in measurable ketosis but I've been on induction carb levels (for optimum health reasons) and very high fat/ moderate protein for over two years. So what's actually happening in my mitochondria. Are ketones necessarily involved. I realize a few kinds of tissue need (some) ketones if glucose is not available - brain for instance. But what about the rest?
Help! I really want to understand this.
Confused

Quote:

Originally Posted by fatburner

My understanding is that fat can be metabolized directly in the Mitochondria, without first converting it to Ketones...and that ketones are created only in specific situations (to feed the Brain, when there is inadaquete oxalacetate, when too much fat is being burned too quickly, etc...)

http://www.unisanet.unisa.edu.au/08366/h%26p2fuel.htm

Quote:

Fatty acids are mobilised from triglyceride stores and used for ATP production, either directly or via the formation of the water soluble ketone bodies.

http://www.unisanet.unisa.edu.au/08366/h%26p2fat.htm

Quote:

An alternative method of utilising the acetyl CoA formed by ß-oxidation is via the synthesis and subsequent oxidation of four-carbon units known collectively as ketone bodies.

Acetyl CoA is converted in the liver into acetoacetate (essentially two acetyl groups covalently linked). Acetoacetate can be further reduced to form ß-hydroxybutyrate. These two compounds are referred to as ketone bodies. Their synthesis occurs in the liver.

They diffuse from the liver into the circulation and are used as fuels by several tissues. Heart muscle and renal cortex, in particular, use acetoacetate in preference to glucose. In contrast, glucose is the major fuel for the brain and erythrocytes in a human on a balanced diet. The brain has the capacity to adapt to the use of acetoacetate during starvation (and in the metabolic disease diabetes mellitus). In starvation of long standing, acetoacetate meets more than 70% of the energy needs of the brain.

This ability of the brain to adapt to the use of acetoacetate is important because fatty acids cannot enter neural tissue. Acetoacetate is regarded as a water soluble and readily transported form of acetyl CoA.

[QUOTE=cc48510]My understanding is that fat can be metabolized directly in the Mitochondria, without first converting it to Ketones...and that ketones are created only in specific situations (to feed the Brain, when there is inadaquete oxalacetate, when too much fat is being burned too quickly, etc...[QUOTE].

Many thanks. That cleared it up for me. I was always a bit puzzled by the oft stated assumption that very low levels of carbs would necessitate constant high use of ketones ( rather than just a trickle to keep the brain purring). It was amusing to read one of your quoted biochem texts describing the low carb state of the brain becoming adapted to using mostly ketones as 'long term starvation' . I have never felt as if I was starving! . Hmmmm? can I be bothered going to the fridge for another helping of chocolate mousse(.3g cho/ serve :p ) ?
One other question. I can see how using ketones is a very energy inefficient (desirably so for weightloss) process. But once your mitochondria get accustomed to FFA metabolism (ie. fat metabolism without ketones)- even during intense exercise (my endurance and strength is far superior now to when I was High complex carb/protein, and I never 'refeed' ) it's actually a very efficient process isn't it? Which might explain why people with a lot of weight to lose find it more and more difficult to do so, the longer they spend low carbing. I'm sure it's still the healthiest and the easiest way to do so (particularly because you just don't get the artificial insulin related 'carb hunger') but would be quicker if the 'metabolic edge' did not reduce the longer a person spent low carbing.

Quote:

Originally Posted by fatburner

One other question. I can see how using ketones is a very energy inefficient (desirably so for weightloss) process. But once your mitochondria get accustomed to FFA metabolism (ie. fat metabolism without ketones)- even during intense exercise (my endurance and strength is far superior now to when I was High complex carb/protein, and I never 'refeed' ) it's actually a very efficient process isn't it? Which might explain why people with a lot of weight to lose find it more and more difficult to do so, the longer they spend low carbing. I'm sure it's still the healthiest and the easiest way to do so (particularly because you just don't get the artificial insulin related 'carb hunger') but would be quicker if the 'metabolic edge' did not reduce the longer a person spent low carbing.

At least from my personal experience, that seems to be somewhat true. My weight loss slowed down considerably (3.5 lbs/wk to 1-2 lbs/wk) almost overnight when the strips stopped turning. Since then, its slowed down to about 1/2 lb/wk, but that was far more gradual.

Keep in mind that as you lose weight, your body need far fewer calories, so as you approach your goal, you will lose weight slower. At some point, if you don't adjust your calories, you will stall. That is pretty typical on any diet. People get use to eating a certain amount of food and forget to slowly adjust downwards.

In my case, I had to cut out a snack and ramp up the exercise to lose those last 15 pounds. However, once you finally lose all the weight, you can ramp up a bit in your eating to maintenance levels.

At 9 pounds from your goal, I am not surprised you are down to 0.5 pounds per week. Keep in mind though that that is the best way to go for the last 10 anyway!

Brobin

all I have to say is....

all I have to say is that continued studies in the area of nutrition will only continue to support what others have been saying for centuries about the benefits of a low and lower carb intake in a person's daily diet....it all will begin to be more cohesive and make all the sense in the world as time goes on...I am glad this study came out....facts always always speak for themselves

I am excited because there is a lot of research in low carb dieting going on. Believe it or not many researchers are interested in this style now even if they may not be convinced it is benificial to people. The one thing I would like to see changed in all these studies is the variable for measuring effectiveness...weight.

As you all know, when starting a low carb regimine you will drop a lot of water weight initially and dieters eating the same calories on a low carb diet will hold less water than if they were eating a more mixed carb diet. Measuring weight only leads to the counter point that these dieters would just gain the weight back if they started eating "normally" again. A bad argument for several reasons yes, but still annoying.

In all studies like this (testing low carb diets and other means of improving body comp) we need to make body comp testing the standard. Underwater bodyfat testing is becoming more and more available and utilizing such measures before and after these studies would be very prudent. We need to show if body comp is improved on LC relative to MC/HC diets. It is my guess, and I'm sure others, that besides the dryer look and feel a LC diet gives, there is a better fat reduction effect of LC dieting.

Quote:

Originally Posted by msundi83

In all studies like this (testing low carb diets and other means of improving body comp) we need to make body comp testing the standard. Underwater bodyfat testing is becoming more and more available and utilizing such measures before and after these studies would be very prudent. We need to show if body comp is improved on LC relative to MC/HC diets. It is my guess, and I'm sure others, that besides the dryer look and feel a LC diet gives, there is a better fat reduction effect of LC dieting.

I agree. The protein sparing diets are all very low carb..the key is to keep the protein macro high and the calories low for the best body composition re losing fat vs losing LBM while losing 'weight.'

The amount of calories isn't as important as the amount of hunger: Carbs stimulate a large insulin response. Insulin is a growth factor for adipose(fat) tissue. The result is, insulin makes you quite hungry (they give insulin to treat anorexia.)

How do you go about tracking your metabolism? I thought measuring your metabolism was something that could only be done in a lab. Not so?

Reading through this thread makes me realize that this board used to know a lot more about metabolism than it currently does.

Nice reading this thread again.

Quote:

Originally Posted by Samuel

Temprature inside our body must be the same no matter which diet we are on.

FWIW, my temperature tends to run between 96 and 97 deg F, at least in the morning when I measure it. Assuming I'm not a completely weird case & that I'm also healthy (the latter, at least, seems to be so), it follows that different people have different temperatures. This wasn't always true, my temp used to be in the standard 98.6 range, but it dropped some years ago, I don't know why.

Beth

Quote:

Originally Posted by LC FP

Reading through this thread makes me realize that this board used to know a lot more about metabolism than it currently does.

That struck me too LC.

Stuart

Quote:

Originally Posted by Beth1708

A low basal temperature (first thing in the morning) could indicate hypothyroid. :idea: