T Nation

Does It Really Matter What You Eat?

First off, I want to make it crystal clear I am not calling any idea dumb. I am simply trying to understand how things work.

So I’m in my physiology class, and I see a chart of the metabolic pathways of the human body. It was amazing what your body can create from what it has.

So while I’m sitting there, I start to question why it should REALLY matter if you are on a predominantly fat or predominantly carb diet, or if the carbs have a low GI. Your body is more than capable of getting its carbs from its own fat stores, and as long as the caloric intake is equal to your needs, there shouldn’t be a problem. Combine your designated amount of fat and/or carbs, supply the body with all the amino acids it needs to create muscle, and there shouldn’t be a difference, right?

Now I think some of my answer has to do with insulin levels, but try as I might I cannot get enough info off the net on what that answer is.

If someone can tell me what the difference is between eating available carbs and turning body fat into carbs, I would really appreciate it.

Thanks,
Meatwad

[quote]Meatwad8 wrote:
First off, I want to make it crystal clear I am not calling any idea dumb. I am simply trying to understand how things work.

So I’m in my physiology class, and I see a chart of the metabolic pathways of the human body. It was amazing what your body can create from what it has.

So while I’m sitting there, I start to question why it should REALLY matter if you are on a predominantly fat or predominantly carb diet, or if the carbs have a low GI. Your body is more than capable of getting its carbs from its own fat stores, and as long as the caloric intake is equal to your needs, there shouldn’t be a problem. Combine your designated amount of fat and/or carbs, supply the body with all the amino acids it needs to create muscle, and there shouldn’t be a difference, right?

Now I think some of my answer has to do with insulin levels, but try as I might I cannot get enough info off the net on what that answer is.

If someone can tell me what the difference is between eating available carbs and turning body fat into carbs, I would really appreciate it.

Thanks,
Meatwad[/quote]

I may be wrong here,but my understanding is the body can NOT convert fat into anything but fat. It can be used as energy by the muscles, but that is it. Protein can be broken down to either glucose or fat and carbs can be broken down to either glucose or fat.

The physiology is way to complex to answer your questions in this type of forum. I am fairly confident in saying though, that your assertion that the body can get its carbs from fat is misguided.

Carbs are a most necessary nutrient, and I wouldn’t make such a jump as too assume that you’ll get the required bodily functions from your plan-o-gram.
Your brain alone consumes more glucose than your muscles ever will.

Anyways, any dr.s or physiologists can correct me if I’m way off base. I am neither--------but I did sleep in a Holiday Inn Express 2 weeks ago.

doesn’t your liver pretty much have a daily maxium production of glucose from protein - something like 100g per day which is equal to or very close to what your brain consumes in a day?

If your body couldn’t convert fat into carbs, you wouldn’t lose weight via Atkins. The way I understand it, it will force your body into ketosis, but once again I don’t know what this does on a less drastic level than atkins, where there is still readily available carbs, just a smaller amount of them.

I could be wrong, can someone tell me where the flaw is in my thinking?

Meatwad

[quote]sasquatch wrote:
Carbs are a most necessary nutrient, and I wouldn’t make such a jump as too assume that you’ll get the required bodily functions from your plan-o-gram.
Your brain alone consumes more glucose than your muscles ever will.
[/quote]

There is no such thing as an essential carbohydrate. Essential and optimal, however, are totally different…

You don’t “need” any carboydrate, your body can use fat to make glucose. It can use protein and burn carbon skeletons from protein too, if I’m not butchering my biochemistry. You only “need” essential amino acids, essential fatty acids (hence the names) and water. Vitamins and minerals and what not too…

The reason the kind of carbs matter has to do with their physical and hormone altering properties. For instance, some carbs are absorbed quicker because they have more surface area, like liquids or fine powders. Some are “roughage” (fiber is still a carb) and have physical effects in the gut.

Various foods have an effect on various hormones. Insulin, GH, IGF, aldosterone and others. This is one of the reasons why eating pop tarts and pepsi will tend to make you greasier then spinach and apples. (Along with the rate of digestion/assimilation, bulk in the stomach, phytochemicals, etc.)

There are other reasons/physiological effects that make certain foods do what they do. These are just a couple off the top of my head.

Interesting topic, look forward to seeing where this goes.

By the way, read the anabolic diet thread for a little more info about fueling with fats vice carbs.

Hope this is the link…

http://www.t-nation.com/readTopic.do?id=658379&pageNo=47#767001

WHOA, guys!

You are already proceeding down an incorrect path:

The human body has no way to convert fatty acids to glucose!

Read this Module:

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

You can certainly produce ENERGY from fatty acids…

Glucose CAN be made from protein (and is)…

Weight loss from Atkins (if it occurs) is because of ultimately being hypocaloric…

Mufasa

[quote] Protein can be broken down to either glucose or fat and carbs can be broken down to either glucose or fat.
quote]

Can protein and carbs really be BROKEN DOWN into fat?? I know it can be stored as fat on a calorie + diet but broken down??

Please enlighten me!

Claes

I think the problem here is that he/she is misusing the word ‘carb’. Either that or I should have paid more attention in my anatomy class.

hi, my first post.
body cannot converte fat into glucose. but into ATP and this actually is the muscle fuel. it can be produced from carbs and protein as well as fat.
they are all just substrates for the production of ATP which is the “energy currency” of nearly any living organism.

regards
eatthis

Whether or not it really matters, a lot of people find it easier to lose fat if they reduce their carbohydrate intake.

This may be especially true in those that are insulin resistant, meaning that insulin levels stay higher for longer after a carbohydrate meal.

This is because though the body can follow many pathways, the pathways that it actually follows is dependent on the hormones present at any point in time. So, what you eat can affect your hormones and have an impact on your goals.

Obviously, if you are starving yourself, you will lose fat (and muscle). Many around here fight tooth and nail to hang onto muscle, so methods other than starvation are used to coax the body to burn off fat… reducing carbohydrate intake is one of those coaxing methods.

Obviously, for those that are already lean, this is probably not something they need to worry about.

[quote]Mufasa wrote:
WHOA, guys!

You are already proceeding down an incorrect path:

The human body has no way to convert fatty acids to glucose!

Read this Module:

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

You can certainly produce ENERGY from fatty acids…

Glucose CAN be made from protein (and is)…

Weight loss from Atkins (if it occurs) is because of ultimately being hypocaloric…

Mufasa

[/quote]

Here’s a paste from this (http://web.indstate.edu/thcme/mwking/gluconeogenesis.html) link:

Oxidation of fatty acids yields enormous amounts of energy on a molar basis, however, the carbons of the fatty acids cannot be utilized for net synthesis of glucose. The two carbon unit of acetyl-CoA derived from b-oxidation of fatty acids can be incorporated into the TCA cycle, however, during the TCA cycle two carbons are lost as CO2. Thus, explaining why fatty acids do not undergo net conversion to carbohydrate.
The glycerol backbone of lipids can be used for gluconeogenesis. This requires phosphorylation to glycerol-3-phosphate by glycerol kinase and dehydrogenation to dihydroxyacetone phosphate (DHAP) by glyceraldehyde-3-phosphate dehydrogenase(G3PDH). The G3PDH reaction is the same as that used in the transport of cytosolic reducing equivalents into the mitochondrion for use in oxidative phosphorylation. This transport pathway is called the glycerol-phosphate shuttle. The glycerol backbone of adipose tissue stored triacylgycerols is ensured of being used as a gluconeogenic substrate since adipose cells lack glycerol kinase. In fact adipocytes require a basal level of glycolysis in order to provide them with DHAP as an intermediate in the synthesis of triacyglycerols.

Now I need to pick up my Biochem primer and reread for myself, as I suggest everyone interested in this topic do.

my book shows a diagram along with explanation that states
Fat is never converted into protein or glucose. The only thing you can do with fat is burn it in the muscle.

This would help explain to the person who asked about the Atkins. Proteins can in fact be broken down into glucose.

[quote]Massif wrote:
sasquatch wrote:
Carbs are a most necessary nutrient, and I wouldn’t make such a jump as too assume that you’ll get the required bodily functions from your plan-o-gram.
Your brain alone consumes more glucose than your muscles ever will.

There is no such thing as an essential carbohydrate. Essential and optimal, however, are totally different…[/quote]

I’ll play along --in the literal sense–but I believe the carbs to be a necesasary nutrient for optimal health. I know short term results are possible without them, but I can’t see a sustained “optimal” health in people who choose to ‘un-carb.’

[quote]Mr. Moose wrote:
Protein can be broken down to either glucose or fat and carbs can be broken down to either glucose or fat.
quote]

Can protein and carbs really be BROKEN DOWN into fat?? I know it can be stored as fat on a calorie + diet but broken down??

Please enlighten me!

Claes
[/quote]

My apologies–broken down into glucose or stored as fat. You sir are correct

[quote]sasquatch wrote:
my book shows a diagram along with explanation that states
Fat is never converted into protein or glucose. The only thing you can do with fat is burn it in the muscle.

This would help explain to the person who asked about the Atkins. Proteins can in fact be broken down into glucose.[/quote]

I think the misunderstanding here is that fatty acids themselves cannot be made into glucose. However, the glycerol backbone, to which they are attached can. This is tricky because we often use the terms “fat”, “lipids” “triaglycerides” and “fatty acids” interchangeably.

I mean no malice and find this whole thread intriguing. Hope we get this whole thing pinned down so I can rap my lil head around it.

-Conor