Dietary fat stored more easily than carbs

K

Karky

2
You know that old thing the low fat crowd used to (and still do) throw around about dietary fat being more easily stored as body fat than dietary carbs? Well, they were right. I came across some papers on de novo lipogenesis (basically the process by which the body can make fat from carbs) maybe 1 year ago or so and it confirmed the fact the low fat crowd was throwing around. The body sucks at making carbs into fat.

So does that mean that fat makes you fat and that you should eat carbs, since they can't turn to fat? That's where the people throwing this fact around in their arguments went wrong.. that's not how it works. Here's my view on the matter that is based on what I currently know. I take my facts here from a review on de novo lipogenesis:De novo lipogenesis in humans: metabolic and regulatory aspects

The more carbs you eat, the more carbs you burn. Your body will simply shift from burning a mixture of fuels to burning almost exclusively carbs on a diet that is high in carbs. Basically, since the body can't make fat from carbs very well, it will store fat as fat and burn carbs during periods of calorie surplus.

If you eat a lot of carbs, your body will turn up de novo lipogenesis some, but it is still very little. But what if you were to eat more carbs than you actually expend during a day? Then you wouldn't be able to just compensate by storing fat and burning carbs. After storing all the fat you could and having all of your energy expenditure resulting form carb breakdown, you'd still have carbs left. And, assuming this goes on for a while so your glycogen stores fill up, where will the carbs go? Will de novo lipogenesis go up significantly in this situation? Or perhaps this situation will result in an urge for more physical activity to burn off the extra carbs? Good studies on eating more carbs than your daily energy expenditure haven't been done, unfortunately. But whether it's increased physical activity or increased lipogenesis, it would result in you being able to eat a bigger surplus, and stay the same weight, than someone overeating with a lot of fat. This simply because increased physical activity would increase energy expenditure and because de novo lipogenesis is an energy expensive process.
So this seems like great news, right? If you are someone that eats a lot, just eat a lot of carbs and you won't get fat as soon as if you ate a lot of fat? (you'd still get fat, though, since you'd have to be in a calorie surplus)

Well, there is a problem there too. Who eats that many carbs? You'd have to eat LARGE amounts of carbs for it to alone cover your energy expenditure.. If you were to keep fat and protein at it's lowest safe proportion while doing so, you'd still have a big of cals from those two, so you'd have to eat a lot. And if you were to cut back on the fat and protein to an unhealthy amount, well, you'd get sick. My point is that this can't be used as an argument for a high carb diet. For any dietary division between P,C,F that actually occurs in real life, de novo lipogenesis would be very, very small, if not non-existing. So even if there was a benefit from eating in a way that promotes de novo lipogenesis no one would ever eat this way, and therefore, the argument posed by the low fat crowd can't be used to blame obesity on high fat diets.

But how does the body change its fuel usage from mixed to mostly carbs, and what consequences does this have in the body? Eating a lot of carbs during the day, you'd have to burn carbs during the night as well (a period when you normally burn a lot of fat), but you don't eat while you sleep, so there must be some kind of mechanism that makes you burn more carbs not only in the postprandinal (right after a meal) but also later when you haven't had anything to eat in a while. The probable way for the body to do this (based on the article, not my reasoning) is that the liver increases its glucose production (the releasing of glucose from the liver). So how does this happen? According to the article, the very full glycogen stores that resulted from the high carb diet can result in increased liver glucose production. But that would lead to increased blood glucose concentrations, which would lead to increased insulin concentrations, and insulin inhibits liver glucose production. One way to fix this is for the liver to become insensitive to insulin (hepatic insulin resistance). Maybe this mechanism can be bad for our health?

This is just one argument the low fat crowd uses. There are more.. for example that with eating fat people have a tendency to overeat more so than when they eat carbs or protein. But I just wanted to punch the whole "your body stores fat more easily than carbs so you shouldn't eat fat" crowd in the face.

I didn't have time (couldn't be arsed with) to specify exactly what is taken from the article and what is my own reasoning, but I put it so that everything that is written in italic is mine and not paraphrased from the article.

Comments?
 
It is rather common for people to get fat eating diets that are very high in both fat and carbs.

Think of all of the high calorie, low other nutritional value foods that are both high fat and high carb -- fries, chips, donuts, anything breaded or batter dipped and fried, pasta with alfredo or other cream based sauces, etc..

For general health, the quality of the fats and carbs probably matters a lot more than the ratio of such in one's diet. Someone who goes low fat might still eat garbage like soda and heavily sweetened breakfast cereals, despite cutting out the junk food that is both high fat and high carb. Someone who goes low carb might still eat garbage like pork rinds and bacon despite cutting out the junk food that is both high fat and high carb.
 
A good article in terms of the fight against fatty foods. On the flip side, a high carb diet greatly increases a person's chance to develop type-2 diabetes, partly because of the fact that in a person that relies primarily on sugars as fuel, their blood sugar levels are higher than normal. Add to the fact that excess calories will still be stored as fat, and we are forced to return to the fact that a balanced macro/micro nutrient diet is normally the best way to go.
 
well, the de novo lipogenesis thing doesn't really have anything to do with ketogenic diets.. I don't get where you're going with that review?
 
maybe i read your article to fast but when you said "So does that mean that fat makes you fat and that you should eat carbs, since they can't turn to fat?" i thought that study (which showed little if any difference fat/carbs effect) and his discussion of that was pertinent to your question.
 
well I guess we could throw all the macro stuff into the discussion, but I was basically just presenting my view on why the fact that de novo lipogenesis is an inefficient and little used pathway in humans can't be used as an argument to not eat fat.

Like I said in my post, I think that if you eat in a way that activates the DNL pathway, you could have a slight metabolic advantage, no one actually eats that way, you'd most likely have to eat more than your entire energy expenditure in carbs.. which would be a lot.
 
Karky said:
Like I said in my post, I think that if you eat in a way that activates the DNL pathway, you could have a slight metabolic advantage, no one actually eats that way, you'd most likely have to eat more than your entire energy expenditure in carbs.. which would be a lot.
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then you have to think about body recomposition,just carbs and no protein isnt going to gain the muscle you would like.

i dont think eating your entire energy source in carbs would be that difficult to be honest,things like potatoes,bread,etc are high in cals and easy to consume.
 
yeah, but who does that?
and this thread isn't about practicality anyway.. it's not about what is done.. it's just about de novo lipogenesis and its implications and I'm saying it has no implications for regular folks.
 
Karky said:
yeah, but who does that?
and this thread isn't about practicality anyway.. it's not about what is done.. it's just about de novo lipogenesis and its implications and I'm saying it has no implications for regular folks.
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kakym not sure if im understanding your point correctly,de novo lipogenesis exists in everyone,its how the body turns carbs into fats,not the other way round.
 
yeah, de novo lipogenesis turns carbs into fat, but it's not an efficient pathway in humans and it isn't active unless you eat A LOT of carbs. Read the article I linked to. It's very good in explaining the research that has been done on de novo lipogenesis.
 
Karky said:
yeah, de novo lipogenesis turns carbs into fat, but it's not an efficient pathway in humans and it isn't active unless you eat A LOT of carbs. Read the article I linked to. It's very good in explaining the research that has been done on de novo lipogenesis.
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basicly its whats been known for a long time,carbs wont turn into fat unless you eat in surplus to your needs,basicly its cals in v cals out no matter what you eat.
 
no, if you eat a surplus but the carbs alone are under your energy expenditure, you won't turn carbs to fat. You'll gain fat, and energy out vs energy in is what counts, but that's not what this article or this thread is about.

to illustrate:
Say your maintenance is 2000kcal, you eat 2000kcal carbs, and 500fat. You'll store the fat and burn off the carbs. But if you eat 3000kcal carbs and 500fat, then your de novo lipogenesis will start to become more active. However, there hasn't been done a lot of research on this situation, so no one really knows exactly what will happen and how that will affect your body. However, it could be speculated that you would gain less weight than if you ate 3000kcal fat and 500carbs, because de novo lipogenesis requires energy (which would, in effect, increase your energy expenditure).

Another point is that as a consequence of the body not turning carbs into fat, it has to change its fuel usage from fat to carbs in periods of high carb intake, and I speculate if that could be bad for your health. It is, for example, associated with liver insulin resistance as an adaptation so that the liver can keep pumping out glucose during the night even though blood glucose and insulin aren't low. The liver has to adapt so that the body burns carbs instead of fat.
 
But if you eat 3000kcal carbs and 500fat, then your de novo lipogenesis will start to become more active. However, there hasn't been done a lot of research on this situation, so no one really knows exactly what will happen and how that will affect your body. However, it could be speculated that you would gain less weight than if you ate 3000kcal fat and 500carbs, because de novo lipogenesis requires energy (which would, in effect, increase your energy expenditure).
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yes but is that to do with DNL or just the fact that your bodies first fuel source is carbs rather than fat (which it tends to hold onto)
 
both, I guess. The reason we use up carbs is because the body sucks at making it into fat, so we have to use it up.

I'm just doing a rebuttal to the low fat diet arguments that use de novo lipogenesis as an argument to eat almost no fat because fat gets stored and carbs don't turn to fat.

I was just spreading some knowledge around the forum.
 
Karky said:
both, I guess. The reason we use up carbs is because the body sucks at making it into fat, so we have to use it up.

I'm just doing a rebuttal to the low fat diet arguments that use de novo lipogenesis as an argument to eat almost no fat because fat gets stored and carbs don't turn to fat.

I was just spreading some knowledge around the forum.
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thats :cool:
also fat is a very efficient energy source for the body,i read somewhere that you could walk 35miles and only use up 1lb of fat,so maybe its still true what they say about us living in stoneage bodies,that would have been quite handy back then :p
 
buzz you're totally not focusing on the point of this article. You're just arguing different things that, while some are true, are not the reason why this thread was made.

Anyway, Karky, on the topic of increased glucose release from the liver, I don't think that would matter as far as insulin resistance and development of diabetes unless you were in a surplus. I realize that your insulin will increase, but like you said, increased insulin will provide a negative feedback for the glucose release. Your body will only release what you need, so I doubt that your serum glucose would remain dangerously elevated. In short, in a caloric deficit or maintenance, you will burn what you take in, so that point becomes irrelevant. I would think, at least.

Let me also add another point in here. Note that your body holds about 200-500 grams of total glycogen stores maximally, depending on body size etc.
"Conversion of carbohydrate into fat allows animals to build
up fat reserves even when their feed contains very little fat. In
adult humans such de novo lipogenesis is primarily a hepatic
process (5). Quantitatively, this conversion plays an insignificant
role in adults consuming mixed diets (1 1). Even after
ingestion of 500 g carbohydrate, the nonprotein respiratory
quotient (RQ) (ie, the ratio of CO2 produced to 02 consumed
by carbohydrate and fat metabolism) does not rise above 1.0,
which indicates that fatty acids are being synthesized at a rate
exceeding the concomitant rate of fat oxidation (Figure 1)
(12). Thus, unusually large, occasional carbohydrate loads are
handled primarily by converting the absorbed glucose into
glycogen. The niassive expansion of the glycogen stores then
leads to the nearly exclusive use of glucose as a fuel (as
shown in Figure 1 by the fact that the RQ remains close to
1.0 for many hours), in time reducing such temporary accumulations
of glycogen. To induce substantial rates of carbohydrate
conversion into fat, the body’s total glycogen
stores must be considerably raised, from their usual 4-6 g/kg
body wt to > 8-10 g/kg body wt. This requires deliberate
and sustained ovenconsumption of large amounts of carbohydrates
for 2-3 d (13)."
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Also:
" When the glycogen stores had increased by ~ 500 g
(end of day 2 of overfeeding), carbohydrate oxidation
and storage became insufficient to dispose of all of the
ingested carbohydrate. The excess was disposed of by
conversion to fat, ie, de novo lipogenesis."

That point is in reference to this:

"During the overfeeding period (days 4-10 inclusive) the
high-carbohydrate, low-fat diet provided -ı- 1 5 MJ (3600 kcal,
composed of 1 1% protein, 3% fat, and 86% carbohydrate) on
day 4. Energy intake was then increased progressively each day
while the composition was kept constant to provide 6.28 MJ
(1500 kcal) in excess ofthe previous day’s energy expenditure,
which was measured in the respiration chamber (8). By day 10
the energy intake had thus increased to ‘-‘21 Mi (5000 kcal)."
Click to expand...


You would have to eat A LOT of carbs to increase DNL to any significant degree. It's almost (not impossible, but still) unthinkable.

As for gaining less weight eating say 3000cal from carbs and 500cal from fat vs. 2000cal carbs and 500cal fat, I, personally, don't think there's a snowballs chance in hell that would happen. The increased energy expenditure will (I'm speculating here) be nowhere near enough to compensate for the caloric difference. Now, you could probably argue your point in a much smaller difference, i.e. 2300cal from carbs and 500cal from fat, but then you have another issue - how much is DNL really increased at that point?
 
I don't quite get what you're getting at. Did you read my thread fully?

I'm not saying that the speculated metabolic advantage of inducing de novo lipogenesis would prevent you from getting fat. Like I said, it might slow down the process, but by how much would be pure speculation, it could be as little as 100grams of fat per year for all I know.

I also said that no one will ever eat in such a way as to induce de novo lipogenesis, so even if there is a significant metabolic advantage to it (something I doubt, and even if there was, you'd have to eat in a calorie surplus for it to happen, so you'd still gain fat, just slower) it is highly unlikely that anyone will actually experience it under normal conditions.

As for the main point here, that eating a lot of carbs will shift your fuel usage from mixed to mostly carb:
liver insulin resistance is seen in diabetics, which is why I say that the liver insulin resistance induced by a lot of carbs in the diet could be bad for your health.
The point here is that the negative feedback of insulin on glucose release from the liver will be decreased with liver insulin resistance (it is the consequence of liver insulin resistance. Insulin decreases glucose release from the liver, but with a lot of carbs, the liver can become resistant to this effect). This would have to happen for the body to use mostly carbs as energy. If it didn't, the body would go back to a mixed fuel usage in the post-absorptive state (I think that's the correct usage of the term, tell me if I'm wrong.. I'm a bit sketchy on the digestion status terms).

My point with this thread is that: 1. the metabolic advantage (if it exists, I think it does) would NOT happen in normal individuals because no one eats such an extreme diet, and even if someone actually ate that way, it would most likely be slight.
2. eating high carb (doesn't have to be so much as to induce de novo lipogenesis, just enough to force the body to use a lot of carbs for fuel instead of a mix) will make the body shift from a mixed to a mostly carb fuel usage, which can be argued to have bad consequences on health.
 
Yes, I did read the whole thread. And I know what your points are, and on those 2 counts I think you are right. I was just adding more info to the fact that the diet to increase DNL significantly is totally unreasonable.

On insulin resistance:
I see your point, I just don't think that would happen in someone who is not diabetic and is in a caloric balance, no?
 
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