de novo fat synthesis from carbs

[stevie]

i am coming to understand that fat gain/loss is simply a result of hyper-/hypo- calorific diet.

but...
something i recently read informed me that there is very little 'de novo' fat synthesis from carbohydrate intake. (How true is that statement?) Carbs in the diet are used for energy, and as such, the excess fat intake over and above calorie requirments is stored.
Since there is very little de novo fat synthesis from carbohydrate, is storage of the fat taken in through the diet the only means of gaining fat?
hypothetically, if you could eat a diet with NO fat (ignore malnutrition/poor hormonal profile issues etc) would a carb intake that provided excess calories still result in fat gain? (eg consume nothing but whey powder and sugar to total a calorie intake in excess of maintainance requiremnets)

ive had a really heavy day, so please excuse me if this is a really dumb question. ill probably ead it tomoroow and wonder what on earth i was thinking.

the only response i can think of at the momnet is that there is very little de novo fat synthesis from carbs UNTIL glycogen stores have been filled. After which fat will be readily synthesised from carbs.

 

[virtualcyber]

After the fat cells and muscle cells FILL up, the liver & fat cells will coordinate with each other to start lipogenesis. I believe the amount of carb comes to about 12 - 14 g / lb of body weight (or is it lbm?).

Check out www.avantlabs.com forum. Do a search on Advanced Section. Look for lipogenesis, etc. Also, you can look at Diet section. The topic has been beaten to pulp.

 

[micmic]

Glucose (and aminoacids) give Acetyl-CoA, which is used for Palmitic acid synthesis, which is a fatty acid (can be converted to other fatty acids).

Fatty acid synthesis is greatly regulated by the enzyme Acetyl-CoA-carboxylase. Besides allosteric regulation, this enzyme is also regulated by diet. If we eat lots of carbs and very few fat, production of this enzyme goes up => fatty acid synthesis increases.

There are other mechanisms too, the bottom line is that excess carbs will convert to fat in a very dissapointing way.

 

[Aaron_F]

If yor eating large amounts of carbs with no fat, de-novo cranks into gear and produces more fat

 

[jsraaf]

Quote[/b] (Aaron_F @ July 14 2003,3:44)]If yor eating large amounts of carbs with no fat, de-novo cranks into gear and produces more fat

You mean, for an extended period of time, longer than your typical carb-up/refeed situation.... right?

 

[Aaron_F]

there will be some on a refeed, but yes, it will ramp up over a few days

but who eats 0g fat on a refeed?

 

[Dianabol]

Dear Stevie,

You have answered your own question when you ended your post with "the only response i can think of at the momnet is that there is very little de novo fat synthesis from carbs UNTIL glycogen stores have been filled. After which fat will be readily synthesised from carbs."

In essence, this is true, in that once your glycogen stores are full, glucose (and other monosaccharides) in excess of blood glucose homeostatic levels (at or around 5mm) will be stored as fat. Excess glucose results in excess citrate and the excess citrate spills out of the TCA cycle, and via the citrate cleavage pathway gets synthesized into the fatty acid palmitate.

Your liver also produces LDLs from dietary glucose (yes, that's how the "bad" cholesterol comes about... dietary glucose) and from there the LDLs are transported in blood to adipose tissue. These two mechanisms, by decreasing blood glucose levels via storage of excess glucose as fat, support glucose homeostasis.

Should you be on a hypocaloric diet, all else being equal you will experience weight-loss. The macronutrient ratios and the individual's insulin sensitivity determines to what extent such weight-loss will be. Because not all carbs are created equal there is interest in the GI and II of carbohydrate foods. As an aside, protein foods have interesting values on the II scale so insulin control on a no-carb diet must perhaps, be more stringent or perhaps revised if such theory is to work in practice. Of interest might be this website:

http://venus.nildram.co.uk/veganmc/insulin.htm

A search on the Insulin Index will provide further reading if you so wish.

Godspeed, happy refeeding and happy HSTing

 

[Aaron_F]

Quote[/b] (Dianabol @ July 15 2003,5:16)]Your liver also produces LDLs from dietary glucose (yes, that's how the "bad" cholesterol comes about... dietary glucose) and from there the LDLs are transported in blood to adipose tissue.

Sorry, doesnt happen that way.


LDL isnt released from the liver

After uptaking the remainding chylomicrons from the blood stream the liver will eject additional cholesterol/FA into the blood stream in VLDL particles. Once these float around in the blood, some of the fats are taken off and this will form IDL, which released some more fats around and becomes the lovely HDL. Theres also an interconnecting sets of proteins that are shared around via these particles, but thats a different story.
THe fatty acids that are carreid in the VLDL particles are PREDOMINANTLY those delivered to the liver by the chylomicron reminants. Sure to some extent some of hte fats will be from hepatic denovo lipogenesis, but this is a minute pathway in humans.

 

[mikeynov]

'Should you be on a hypocaloric diet, all else being equal you will experience weight-loss. The macronutrient ratios and the individual's insulin sensitivity determines to what extent such weight-loss will be. Because not all carbs are created equal there is interest in the GI and II of carbohydrate foods. As an aside, protein foods have interesting values on the II scale so insulin control on a no-carb diet must perhaps, be more stringent or perhaps revised if such theory is to work in practice. Of interest might be this website:'

My understanding from reading diabetic literature and such that aaron had posted was that GI/II issues were sort of inconsequential if a diet were hypocaloric.

So I suppose here's my question:

assuming fixed amounts of identical fat/protein (adequate in both cases to support what we're aiming for), what would happen in the following situations in respect to fat gain or loss:

1) hypocaloric diet composed of low GI/II carbs vs. high GI/II carbs
2) normocaloric diet composed of low GI/II carbs vs. high GI/II carbs
3) hypercaloric diet composed of low GI/II carbs vs. high GI/II carbs

 

[Aaron_F]

Unfortuantely an absolutely impossible situation, outside of a metabolic ward. Would be a nice experiment. But

OVerfeeding of glucose, sucrose, fat all equates to an equal weight gain

Maintenance is just that, maintenance.

Hypocaloric, even if you eat pure glucose, you can lose weight. And there is no data showing any advantage between low and high GI foods this way (and most would be a mix of low and high II)

But, in the real world, there is potential that high II/GI foods will create a drop in blood sugar, increasing hunger. So you eat more, therefore lose less weight or gain more.

Worrying about proteins affect on insulin is of little consequence anyway, because it also raises glucagon, so the overall ratio of I:G doesnt relaly change.

 

[Aaron_F]

Unfortuantely an absolutely impossible situation, outside of a metabolic ward. Would be a nice experiment. But
OVerfeeding of glucose, sucrose, fat all equates to an equal weight gain
Maintenance is just that, maintenance.
Hypocaloric, even if you eat pure glucose, you can lose weight. And there is no data showing any advantage between low and high GI foods this way (and most would be a mix of low and high II)
But, in the real world, there is potential that high II/GI foods will create a drop in blood sugar, increasing hunger. So you eat more, therefore lose less weight or gain more.
Worrying about proteins affect on insulin is of little consequence anyway, because it also raises glucagon, so the overall ratio of I:G doesnt relaly change.
Im sick, so Im about to go home

 

[micmic]

I think mikeynov was asking whether there would be any difference in the muscle/fat ratio of the gains or losses. The weight gain/loss would of course depend only on ingested calories.

Even if it were possible to exactly produce high or low sugar/insulin responses, I wouldn't expect any difference. In a bulking diet for example, the more anabolic stimulus would also be more lipogenic. In essence, the question is the same as 3 big meals vs 6 smaller ones. I'm not aware of any data clearly favoring one over the other.

 

[mikeynov]

Quote[/b] (Aaron_F @ July 15 2003,4:04)]Unfortuantely an absolutely impossible situation, outside of a metabolic ward. Would be a nice experiment. But
OVerfeeding of glucose, sucrose, fat all equates to an equal weight gain
Maintenance is just that, maintenance.
Hypocaloric, even if you eat pure glucose, you can lose weight. And there is no data showing any advantage between low and high GI foods this way (and most would be a mix of low and high II)
But, in the real world, there is potential that high II/GI foods will create a drop in blood sugar, increasing hunger. So you eat more, therefore lose less weight or gain more.
Worrying about proteins affect on insulin is of little consequence anyway, because it also raises glucagon, so the overall ratio of I:G doesnt relaly change.

aaron, the question wasn't simply one of 'weight gain' or 'weight loss.' i'm talking %'s here, eg what would the effect be in respect to partitioning towards the p end of the p-ratio (as far as i know, this idea extends to both hypo and hyper caloric scenarios).

example: adequate protein shifts the p-ratio a bit away from fat gain/muscle loss, depending on calories. two diets can yield the same net 'weight loss' but carry different ratios of loss of muscle vs. fat. obviously this logic extends to encompass both protein and fat ('enough' of both affecting such partitioning as far as i know), but NOT carbohydrates?

you project NO difference based on carbohydrate intake for any of the three scenarios i presented? in a way, this contradicts my own anecdotal experience as well as that of the past 50 or so years of bodybuilding. i would THINK that there would be partioning issues based on insulin response to 'type' of carbohydrate intake, but i suppose i could also be mistaken.

i mean, insulin sensitivity certainly relates to fat accumulation. though the article you posted a while back seemed to indicate that insulin resistance was primarily a result of excess calories, rather than carbohydrate type. dianabol and i had previously discussed the mechanisms involved in IR where adipose tissue ends up footing the bill as both become insensitive to the effects of insulin. would not high GI/II index carbs in the long run exaggerate insulin resistance in somebody on a hypercaloric diet, in turn partitioning calories towards the fat end of the spectrum?

the only thing you point out that makes the most sense to me is that carbohydrate 'type' relates to hunger control mechanisms, eg one is more likely to overeat high GI/II carbs than low GI/II if not monitoring kcals and basing eating on their own satiety. i suppose i'm just looking for clarity on some of these issues

 

[virtualcyber]

mikey:

As per high GI or low GI carbs, Aaron is probably right. Others who know something about this area says the same thing: for "normal healthy" folks, GI does not make much difference, as long as identical calories are consumed. (Lyle McDonald, Elzi Volk, Robert Thoburn, etc.) on lipogenesis. This basically means GI of ingested carb has little impact on overall bf%.

If you do a search on pubmed, you will find little evidence to support the position that GI makes any difference to overall body composition.

Also, it is well known that increasing protein intake promotes anabolism; I don't think Aaron is arguing this point.

 

[mikeynov]

Quote[/b] (virtualcyber @ July 15 2003,6:42)]mikey:
As per high GI or low GI carbs, Aaron is probably right. Others who know something about this area says the same thing: for "normal healthy" folks, GI does not make much difference, as long as identical calories are consumed. (Lyle McDonald, Elzi Volk, Robert Thoburn, etc.) on lipogenesis. This basically means GI of ingested carb has little impact on overall bf%.
If you do a search on pubmed, you will find little evidence to support the position that GI makes any difference to overall body composition.
Also, it is well known that increasing protein intake promotes anabolism; I don't think Aaron is arguing this point.

i know, but this still doesn't entirely make sense in my mind.

i could see the argument that GI/II don't matter as much at or below maintenance. there's research even demonstrating that the insulin resistant respond BETTER to hypocaloric diets. ie even if high GI/II created some sort of local IR phenomenon, this wouldn't necessarily be detrimental.

however, after discussing this issue with others (including dianabol), i HAVE to imagine there's a strong case to be made that if you're eating HYPERCALORICALLY, carb type should help partitioning in respect to the p-ratio. i always look to 'science first' to help explain the natural world around me, but what's being offered seems to contradict anecodte so strongly that it leaves me feeling a bit skeptical. i'm not sure exactly what it was, perhaps subconscious eating habis due to satiety, but when i simply switched from shittier refined carbs to lower GI/II carbs (all else constant), my body composition changed noticably.

I mean, we're basically arguing that a bodybuilder could get as ripped on vanilla coke and fruity pebbles as he could on brown rice and oats. this strikes me as contrary to a half century worth of accumulated anecdotal wisdom

 

[virtualcyber]

mikeynov:

I understand your position

There is one more factor in the equation: most of today's sugary food contains fructose. fructose (and sucrose) is much more likely to initiate lipogenesis than other complex carbs. GI of fructose, interestingly enough, is very high.

One more thing -- carbs can be absorbed by the fat cells before the initiation of lipogenesis. This causes bloating, which some people seem to mistake for lipogenesis. It doesn't matter, I suppose, because the absorption signals impending lipogenesis anyways.

 

[micmic]

Quote[/b] ]fructose (and sucrose) is much more likely to initiate lipogenesis than other complex carbs. GI of fructose, interestingly enough, is very high.

Fructose is not a complex carb
Fructose is low GI
Fructose will not be more lipogenic when everything else is taken inro acount. It will not convert to triglycerides until you eat more than 60gr daily. And even if it does, net fat gain/loss will be a function of total calories.

 

[virtualcyber]

micmic:

(1) I did not mean fructose is complex carb.

(2) I was mistaken about its glycemic index (confused).

(3) lipogenesis -- I hope you expand on what you said. From what I gather, if one is carb depleted, one can consume about 12 g - 14 g of carb per lb of weight (or lbm?), if one is consuming maltodextrin before lipogenesis can begin.

I think if you are consuming fructose, lipogenesis occurs a lot sooner than that (before 12 g / lb is reached). Also, I am not sure 60 g figure is not accurate, in the sense that it depends on the degree of one's state of glycogen depletion.

(3) Finally, as per steady state production of fat, I agree it depends on one's steady state consumption of food calories; in the long run, it won't make any difference whether you are consuming fructose or not.

Will eating fructose initiate lipogenesis sooner than eating other types of carbs (assuming equal calories)? I think the answer is yes.

 

[micmic]

Let's assume that the energy requirement of one person is 100 kcal for a certain amount of time. Also, let's assume liver is full of glucogen. He eats 25gr glucose, he covers his needs. He eats 25gr fructose, it's converted to fat, but in the absence of carbs he will burn this fat.

Also see this.

 

[virtualcyber]

micmic:

If the above is the case you are talking about (in which fat burning catches up with lipogenesis) then we are in agreement.

But there are other scenarios. One scenario involves refeeds in CKD. Here, we are trying to push the limits of glycogen storage without fat creation during refeeds (i.e., during caloric surplus); this way, you can _maximally_ use stored glycogen during high intensity exercise.

This becomes more relevant in maximizing lbm retention.