PDA

View Full Version : Low-carb, High-protein Diets, Why?



Jorge Sanchez
08-07-2006, 04:56 PM
In the context of a weight loss diet, I see no advantage to taking out carbs and replacing them with protein. That said, I have a limited understanding of nutrition so I want to see if there is any logic behind it.

Protein is used primarily to build and maintain body tissue. Once the body reaches a threshold where the need for amino acids is met, additional protein is converted to glucose, glycogen or fat for immediate energy and storage.

The nervous system, brain and various other organs require glucose to function. The body's primary source of glucose is carbohydrates. If the body does not receive sufficient glucose from carbs and the liver's glycogen stores are depleted, the body will convert excess protein to glucose rather than resort to ketosis. In the absence of carbs, protein becomes the primary source of glycogen.

So:

1) What is the advantage of consuming more protein than necessary for the maintenance of lean tissues? Once the threshold is met, will lean tissue not be preserved?

2) Why sacrifice carbs, to be replaced by protein, when both carbs and excess protein are destined to become glucose or glycogen? I know built advocates low-carb diets because carbs stimulate her appetite, but is there any other reason to replace carbs with protein?

3) Are carbohydrates not 'protein-sparing' in that they assure a sufficient supply of glucose and prevent the conversion of protein to glucose?

Built
08-07-2006, 05:03 PM
Protein has a higher TEF
Protein is more satisfying
On a cut, protein helps spare LBM

Those are my reasons.

Jorge Sanchez
08-07-2006, 05:07 PM
The first two make sense, but why does excess protein help spare LBM? Once you meet your body's need for protein the excess is converted to glucose or fat.

Since you're not building new muscle wouldn't your protein requirements be lower on a cut than a bulk?

Built
08-07-2006, 05:13 PM
As I understand it, it's higher, since you're under stress.

Slim Schaedle
08-07-2006, 07:25 PM
Protein is used primarily to build and maintain body tissue.
Just curious if these are your words, or if you read them somewhere.

Jorge Sanchez
08-07-2006, 07:47 PM
My words.

Minotaur
08-07-2006, 08:01 PM
There's a problem with using protein as your main fuel source... you teach your body to use protein, and if you miss a meal your body starts to use its own protein for fuel.

If you are not insulin resistant/diabetic, you are better off with a balanced intake of cabrs, protein and fat, something like 40/40/20 or 40/35/25. I myself am doing better on high fat, med. protein, low carb because I am insulin resistant.

Built
08-07-2006, 08:06 PM
What, exactly, is so magical about "balance"?

Why not just dose protein and fat to LBM?

And what do you mean by this:


There's a problem with using protein as your main fuel source... you teach your body to use protein, and if you miss a meal your body starts to use its own protein for fuel.

Slim Schaedle
08-07-2006, 08:06 PM
My words.
As bodybuilders, we are certainly concerned with the function of proteins in relation to its structural functions.

However, the functions include transport proteins, immunoproteins, enzymes, structural proteins, plasma proteins, peptide hormones, protein scretions which include digestive enzymes and endogenous protein, and other non structural proteins and nitrogen containing compounds.

Although much of the body consists of protein, it does not necessarily mean that the main function of protein we ingest is to contribute to that mass.

The answer to your question about the purpose for excess protein pretty much lies within the description above.

Pup
08-07-2006, 08:17 PM
The first two make sense, but why does excess protein help spare LBM? Once you meet your body's need for protein the excess is converted to glucose or fat.

Since you're not building new muscle wouldn't your protein requirements be lower on a cut than a bulk?

The problem, from my point of view, is in your definition of excess. There is no arbitrary amount of protein that you can consume and consider yourself to be "out of the woods" in regards to catabolism and cortison response.

Hormonally, there are several advantages to a reduced carbohydrate diet (specifically if your somatype is geared towards fat storage). First, keeping carbs low will help keep insulin stable, which is a central focus in successful dieting. Second, if carbs are lower, you are able to eat more protein and more fat. More protein means aminos, with more aminos your chances for repartitioning are greater. With more fat, especially EFAs, you increase satiety (crucial while dieting) and the research is pretty substantial in showing high dose EFAs increase metabolic output as well as support cardiac health.

The drawback to lower carbs is T3 conversion, if you have a very low carb diet (<50g per day), you will need periodic refeeds of carbs to increase t3 conversion...some people can do this with a cheat day, others need to show more restraint and eat high amounts of clean carbs.

If you want to view some research on the benefits of low carb diets, I would suggest looking at the work of Volek and Manninen. Rob Faigin's NHE book also has an abundance of research citations that would be worth looking into if the topic is of interest to you.

Jorge Sanchez
08-07-2006, 08:18 PM
As bodybuilders, we are certainly concerned with the function of proteins in relation to its structural functions.

However, the functions include transport proteins, immunoproteins, enzymes, structural proteins, plasma proteins, peptide hormones, protein scretions which include digestive enzymes and endogenous protein, and other non structural proteins and nitrogen containing compounds.

Although much of the body consists of protein, it does not necessarily mean that the main function of protein we ingest is to contribute to that mass.

The answer to your question about the purpose for excess protein pretty much lies within the description above.

I was aware of the other functions (although I couldn't list all of them), but I figured in the context of my post and the weightlifting forum, my 'primarily' would suffice. And I was not necessarily refering to simply muscle tissue, but all other body tissues. I do appreciate the clarification, though.

You are very knowledgeable about nutrition, so did I misunderstand anything else in my original, or any subsequent posts?

MagnaSephiroth
08-07-2006, 11:26 PM
I started somewhat of a carb cycle. When I was eating 2200 (just bumped up to 2400 today) I on heavy days ate about 200g of carbs, 250g of protein and about 55-60g of fat

low carb days I eat as low as 130g of carbs, and closer to 300g of protein. Medium, you can pretty much guess. The only thing constant is fat, at 55-60g a day. I started doing this low/medium/high carb days because of reading builts posts and some site that was linked in a similar thread about this. These levels im doing...they arnt harmful are they?

Built
08-07-2006, 11:55 PM
Magna - I can't see why they would be, although you MIGHT choose to go higher in fat and a hair lower in protein and possibly carb on the lowest carb day. Up to you.

MagnaSephiroth
08-08-2006, 12:29 AM
Magna - I can't see why they would be, although you MIGHT choose to go higher in fat and a hair lower in protein and possibly carb on the lowest carb day. Up to you.

I'm also bulking, and i heard carb cycle reduces fat gains..right?

Built
08-08-2006, 12:49 AM
It's supposed to. It can't do any harm.

Pup
08-08-2006, 07:39 AM
I'm also bulking, and i heard carb cycle reduces fat gains..right?

Any lean bulking type of diet in which calories are cycled will keep down fat gain, as will keeping the protein high, like Built mentioned before, the TEF from protein is high and repartitioning is at a premium when protein intake is substantial. Just take the approach that is easiest and seems the least like its work.

Minotaur
08-08-2006, 10:11 AM
What, exactly, is so magical about "balance"?

Why not just dose protein and fat to LBM?

And what do you mean by this:

Nothing magical about it, just a place to start. Assuming most people have no problem processing carbs, there's nothing wrong with them. Even Dr. Atkins said that endurance athletes should not follow his diet because they need carbs for energy.

If you find you are carb intolerant, then you shift your macronutrients. But it shouldn't be towards protein. I already said it: when you miss a meal, you start burning muscle if your body has learned to use protein for fuel.

The other option is fat, as in a ketogenic diet.

MagnaSephiroth
08-08-2006, 08:46 PM
Any lean bulking type of diet in which calories are cycled will keep down fat gain, as will keeping the protein high, like Built mentioned before, the TEF from protein is high and repartitioning is at a premium when protein intake is substantial. Just take the approach that is easiest and seems the least like its work.

Thank you Yoda

Built
08-09-2006, 03:08 PM
...when you miss a meal, you start burning muscle if your body has learned to use protein for fuel.

This is interesting, and I've never heard this before. Got a source, Minotaur?

Mercuryblade
08-09-2006, 06:19 PM
To answer your question in a really subsinct (spelling?) manner. Built and Slim really know what they are talking about.
But everybody is also different. Use what you have learned from this thread and do some experimenting.

Pup
08-10-2006, 07:27 AM
This is interesting, and I've never heard this before. Got a source, Minotaur?

BUMP!

...I would also like see some research on this, human studies would be phenomenal if you have them.

Pup
08-10-2006, 07:28 AM
To answer your question in a really subsinct (spelling?) manner. Built and Slim really know what they are talking about.
But everybody is also different. Use what you have learned from this thread and do some experimenting.


Succinct...close enough though ;)

lifter4life
08-11-2006, 12:15 AM
The reason is because BBer's keep the protein amount the same amount no matter what on their cut diets (This is to preserve muscle). If a BBer wants to obtain a low bodyfat percentage they have to cut calories, which would come from fats/carbs (They don't take away protein because they want to preserve muscle); this is where you get into wacky ratios like 50/30/20 P/C/F.

Clifford Gillmore
08-11-2006, 12:45 AM
BUMP!

...I would also like see some research on this, human studies would be phenomenal if you have them.

It was in last months copy of Muscle and Fitness... I swear....

Built
08-11-2006, 12:54 AM
<chuckle>

Pup
08-11-2006, 07:27 AM
The reason is because BBer's keep the protein amount the same amount no matter what on their cut diets (This is to preserve muscle). If a BBer wants to obtain a low bodyfat percentage they have to cut calories, which would come from fats/carbs (They don't take away protein because they want to preserve muscle); this is where you get into wacky ratios like 50/30/20 P/C/F.

That still doesn't answer the question though.

Minotaur stated that the body will use protein preferentially as a fuel source. If you have zero calories coming from carbs or fat I can see where this is the case, but otherwise it makes no sense to me. Consider, if you have carbs very low, glycogen levels drop, but the body has a back-up plan in the form of ketones, so you are still getting some form of energy inducing product that will support ATP production. The reverse is also true in that if you have fat low and carbs high the body will use glycogen to support ATP production. Granted, it is becoming increasingly clearer that too low on fat consumption is detrimental not only to metabolic support but cardiac health, etc. You also have the fact that with large amounts of protein you will get gluconeogenesis happening, so there is going to be some glucose in the bloodstream for energy systems balance. In all three cases, you have the body using some form of feedback loop that doesn't involve atrophy to sustain energy system balance. The bodybuilder's pursuit of aesthetics and keeping protein constant has nothing to do with the phenomena that Minotaur is referring to.

The body has one main goal, survival, so if there is some way that the body is actually using cellular building blocks (aminos) even with adequate CHO or fat to sustain energy system balance, its pretty significant.

Pup
08-11-2006, 07:29 AM
It was in last months copy of Muscle and Fitness... I swear....

:bash: