4

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Is Carbohydrate Intake the Primary Determinant of Energy Substrate Utilized for Oxidation?

Answered on August 19, 2014
Created October 03, 2011 at 12:03 AM

Failure of dietary fat intake to promote fat oxidation

I've been thinking a lot lately about the (mostly enzymatic) adaptive return to lipid oxidation that most of us experience as a result of eating an ancestral diet and my gut feeling has been that this has zero to do with how much fat one eats, and everything to do with how much carbohydrate is in the diet and how and when it is eaten. We have a largely fixed pool of glycogen into which we can store glucose. As precious a commodity as glucose is, the body will force the oxidation of excess rather than super-saturating glycogen stores for long or having blood glucose remain elevated overly much.

What this means is that everything basically goes on high alert when starch or sugar is consumed and the body makes that glucose disappear with one means or another. If you eat a potato with a pad of butter vs. a stick of butter, the rate of systemic lipid oxidation is the same. The only difference is that more fat ingested equates to more fat stored in adipose tissue. Our fat stores are massive compared to glycogen stores and as we all know, can swell to great magnitudes to accommodate more of this stable energy.

A chronically elevated fat intake (and thus, an increase in body fat mass) in a hunter-gatherer will eventually result in an increase in metabolic rate that should push the person back to a preferred body fat %. The regulation of this process doesn't appear to have anything to do with day-to-day fat intake, but rather, the amount of fat someone carries and thus the amount of leptin that their adipocytes secrete. I don't see why we paleos living in a land of abundance wouldn't be able to eat enough fat to overwhelm this regulatory system since the hypothalamus can only increase metabolic rate/body temperature so much before hitting a safety ceiling.

The only reliable way to increase lipid oxidation without increasing fat mass as I see it is to increase the volume of low to moderate intensity muscle contraction, and thus the need for energy.

What I keep wondering about though is how often I see people recommend that a fat loss plateau be addressed with more fat being eaten. So many people seem to be in agreement that this is the correct path that there must be some truth to it. How does this work exactly? You eat Diet A and your fat loss stalls, so you eat Diet A + bacon & avocado and you start shedding body fat again? I'm trying to wrap my mind around this concept, but I'm at a loss here. Eating itself raises metabolic rate obviously though the metabolism of food, but the added food would have to result in a net caloric deficit for this to explain the phenomenon. We're not talking about cabbage, we're talking about bacon here. If anyone can point me in the right direction, I would appreciate it.

21fd060d0796fdb8a4a990441e08eae7

(24543)

on October 03, 2011
at 05:51 PM

IMHO, Lyle is right about pretty much everything. I posted a lot on his forum about 7-8 years ago, and he was clarifying the biology of intermittent fasting, ketosis, protein needs, etc a while before then. And he has lots of experience working with clients. And he is a total asshole if you ask a dumb question.

77877f762c40637911396daa19b53094

(78467)

on October 03, 2011
at 05:38 PM

TBH, I don't know a reason why olive oil is considered healthy, especially for skin. I remember Rosedale mentioned that in his opinion its not healthy per se, but its good effects are probably because all other oils are harmful. I find hard to believe that main human fat storage is toxic (SFA).

77877f762c40637911396daa19b53094

(78467)

on October 03, 2011
at 05:36 PM

MCT is saturated fat. I never heard any negative effects of olive oil. Rosedale diet is based on MUFA for instance. Contrary, olive oil has almost sacred status and everything that includes olive in some form is healthy - from leafs that some people chew to virgin oil. I use at least 2 tbsp per day for ages. I will check out the study you mentioned but the problem is, again, it is a HC HF study as they used 100g muesly for breakfast. For instance here is a ketogenic diet study that is using SFA vs PUFA setup. http://jcem.endojournals.org/content/89/4/1641.full

Medium avatar

(39831)

on October 03, 2011
at 04:30 PM

Wow, it's hard to find studies with legitimate fat sources; I'll keep digging.

Medium avatar

(39831)

on October 03, 2011
at 04:06 PM

You make some great points as usual, but around these parts there's a tendency toward advocating an increase in saturated fat specifically, which appears to be oxidized to less of an extent than MCTs of course or even MUFAs http://ukpmc.ac.uk/abstract/MED/12037652 Even so, I wouldn't say that adding olive oil on top of a particular diet would result in a net loss of body fat.

Medium avatar

(39831)

on October 03, 2011
at 03:59 PM

Yeah, I've seen his name mentioned but never really looked at his site. Everything I've read so far seems rooted in biochemistry. I think I'm gonna try to read it all.

C471216c9fb4fcf886b7ac84a4046b49

(1371)

on October 03, 2011
at 02:29 PM

Travis: I tend to agree with lyle on most his writing, it's no bullshit and straight forward

Cbb1134f8e93067d1271c97bb2e15ef6

on October 03, 2011
at 11:58 AM

Changing the macronutrient ration is obviously different from just "adding fat." And in that context, it totally makes sense and I have experienced it to be true. However, the body has an amazing way of adjusting and given time, at least with significantly overweight ppl, more adjustment will be needed.

64433a05384cd9717c1aa6bf7e98b661

(15236)

on October 03, 2011
at 04:02 AM

To some degree it's 'more everything'. I generally eat low-ish carb, though when trying to gain weight I add more sweet potatoes, I tried adding cheese which was fun and tasty but I didn't feel great with it.

Medium avatar

(39831)

on October 03, 2011
at 03:17 AM

Mallory: This Lyle Mcdonald guy seems to agree with me: http://www.bodyrecomposition.com/fat-loss/do-i-need-to-eat-more-fat-to-burn-fat-qa.html

Medium avatar

(39831)

on October 03, 2011
at 02:29 AM

If it's for satiety reasons, doesn't lean, red meat have the best satiety:energy ratio?

3846a3b61bc9051e4baebdef62e58c52

(18635)

on October 03, 2011
at 02:23 AM

As to your question to merideth...I would essentially say that some people who switch to paleo ALSO switch to eating less. They assume that paleo is like any other reductionist diet (we have been taught to reduce calories all our lives). They are wrong, and need to relearn some basic eating principles that they have been taught via media induced modification to forget....eat more good food. So we chime in and say.."dont be afraid"...its ok to eat fat. Usually this helps them reach a homeostatic normal that there previous misconceptions prevent.

667f6c030b0245d71d8ef50c72b097dc

(15976)

on October 03, 2011
at 01:21 AM

Clearly merely adding in more fat to X diet like in your bacon and avocado example couldn't result in losing more weight. I have to think that the people that recommend "more fat!"to bust a plateau assume that the eater will further replace dietary carbohydrate with that new fat; in other words they would be going lower in carbs and as close as possible higher in fat. Hwever since almost none of these people track their food how they could know how close this caloric trade is to even is beyond me.

667f6c030b0245d71d8ef50c72b097dc

(15976)

on October 03, 2011
at 01:18 AM

Exactly what I was wondering: overeating with fats or carbohydrate

Medium avatar

(39831)

on October 03, 2011
at 01:08 AM

Meredith: I'm wondering if the common recommendation (in the paleosphere) to eat more fat to break through a fat loss plateau is actually good advice, and if so, what the mechanism is by which it acts.

Medium avatar

(39831)

on October 03, 2011
at 01:04 AM

Is this overeating in the form of carbohydrates or fats?

7dc950fc76a046048e683d2a27dced37

on October 03, 2011
at 12:53 AM

"So many people seem to be in agreement that this is the correct path that there must be some truth to it." Really? Or is it just attachment to a specific idea?

1f8384be58052b6b96f476e475abdc74

(2231)

on October 03, 2011
at 12:44 AM

homeostasis? i think its lyle mcdonald who had done writing on this...

0dbd7154d909b97fe774d1655754f195

(16131)

on October 03, 2011
at 12:34 AM

I don't totally understand. What I have read is that if there is glucose present, that MUST be disposed of first before fats can be burned. In combination fats are stored so that sugar can be cleared. Sugar in the system is a toxin after all I have been told. So using fats as the primary energy source in the absence of carbs would result in more lipid oxidation I think. Furthermore, shorter chain fats like coconut and monounsaturates like avocado would be easier to break down than say lamb fat. I think I am not totally getting the question though.

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3 Answers

2
77877f762c40637911396daa19b53094

(78467)

on October 03, 2011
at 08:12 AM

To use this study to conclude anything about long term adaptation is meaningless.

Some obvious problems:

  • Nutrient content was calculated by using a food composition table provided by the food manufacturer. This is not strict as with artificial food so who knows what was exact content
  • The subjects were eating more then 300g of CHO daily and they added trans fat on top of that. In the study it isn't mentioned which type of fat they were using rendering study flawed ASAP, but they mention that in their previous study they used 50g of margarine so they probably did the same here. We know that trans fats induce obesity.
  • The study lasted 1.5 days, its not enough for serious fat oxidation changes.
  • The study didn't monitor levels of important beta oxidation substrates like carnitine or vitamin B5.

In short, while I appreciate this study for data generation, they are biased to 'fat-hypothesis' if they can conclude something like that from the methods they used. The situation is guarantied to be different on LC diets. People suggest to other people eating more fat because if you can't really eat much more protein and if you are LC and still hungry, you need more fat to eat as you can't really be hungry and loose/maintain weight. On top of that we now know how this influences microbiota control of fat storage - see fiaf tags at Hyperlipid.

I guess you really need to weight your evidence and read studies carefully. Studies are most of the time wrong. Its best to look at the data yourself and skip the authors conclusions. I would actually, forbid concluding and limit all studies to just data generation.

In my xperience, exercise is not that important for weight loss per se if you don't change your diet to LC HF. Once you do it, it will speed hormone stabilization because of increased metabolic rate. Once you fixed that, you can omit exercise without harm, I think, related to energy balance. Exercise for other reasons - keeping your animal self. My personal XP confirms this and of few of my friends. We all feel far better, and more energetic, but weight doesn't change [although it could be mistake in observation as -fat +muscle but I guess that has to stop one day or you would be Hulk]. I removed all my exercise extra of walking and started to drop weight again.

Medium avatar

(39831)

on October 03, 2011
at 04:30 PM

Wow, it's hard to find studies with legitimate fat sources; I'll keep digging.

77877f762c40637911396daa19b53094

(78467)

on October 03, 2011
at 05:38 PM

TBH, I don't know a reason why olive oil is considered healthy, especially for skin. I remember Rosedale mentioned that in his opinion its not healthy per se, but its good effects are probably because all other oils are harmful. I find hard to believe that main human fat storage is toxic (SFA).

77877f762c40637911396daa19b53094

(78467)

on October 03, 2011
at 05:36 PM

MCT is saturated fat. I never heard any negative effects of olive oil. Rosedale diet is based on MUFA for instance. Contrary, olive oil has almost sacred status and everything that includes olive in some form is healthy - from leafs that some people chew to virgin oil. I use at least 2 tbsp per day for ages. I will check out the study you mentioned but the problem is, again, it is a HC HF study as they used 100g muesly for breakfast. For instance here is a ketogenic diet study that is using SFA vs PUFA setup. http://jcem.endojournals.org/content/89/4/1641.full

Medium avatar

(39831)

on October 03, 2011
at 04:06 PM

You make some great points as usual, but around these parts there's a tendency toward advocating an increase in saturated fat specifically, which appears to be oxidized to less of an extent than MCTs of course or even MUFAs http://ukpmc.ac.uk/abstract/MED/12037652 Even so, I wouldn't say that adding olive oil on top of a particular diet would result in a net loss of body fat.

2
3846a3b61bc9051e4baebdef62e58c52

(18635)

on October 03, 2011
at 12:21 AM

Your at a loss because your rationale is based solely on current science experimentation and not individual case studies....The vastness of human capabilities and physiological capacity will never be completely understood (at least not in your or my lifetime), and our current understanding is even in the most gracious sense mediocre. We obviously have a lot more to learn. Case studies have far more to offer than the scientific realm will currently recognize....RCT's are not the be all end all and have massive limitations in and of themselves.

0
64433a05384cd9717c1aa6bf7e98b661

(15236)

on October 03, 2011
at 12:41 AM

I think to some extent the error is in food reporting. When someone adds bacon and avocado, they are almost definitely replacing something in the diet, and that is often carbs. Also this may be accompanied by a reduced need for snacking.

Also, I think the influence of hunger signaling is also not emphasized enough in any of the calories in/calories out discussions. In GCBC, Taubes mentions feeding studies where people were going to bed hungry on a 10,000 kcal/day diet of carbs whereas people would be staring at a plate of pork chops and refusing to eat.

So to respond to your question about living in abundance, I think the metabolic rate in healthy people does of course increase in response to food increases, but also it becomes harder and harder to overeat.

At 6'0, 145 lbs, my personal experience has been when I all but stop any type of cardio, lift weights, and try to overeat as much as possible I can gain 5 lbs but it's a constant struggle to maintain. My metabolic rate definitely increases, my sleep suffers, and after every 5 days or so of overeating, I wind up having a day or two of eating very lightly and then my weight starts to go back down.

my 2 cents

edit: regarding that study, I'm not sure 2 days/3nights is enough time for people (probably not very fat adapted) to ramp up their fat metabolism?

Medium avatar

(39831)

on October 03, 2011
at 01:04 AM

Is this overeating in the form of carbohydrates or fats?

667f6c030b0245d71d8ef50c72b097dc

(15976)

on October 03, 2011
at 01:18 AM

Exactly what I was wondering: overeating with fats or carbohydrate

64433a05384cd9717c1aa6bf7e98b661

(15236)

on October 03, 2011
at 04:02 AM

To some degree it's 'more everything'. I generally eat low-ish carb, though when trying to gain weight I add more sweet potatoes, I tried adding cheese which was fun and tasty but I didn't feel great with it.

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