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.
asked byTravis_Culp (39831)
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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.
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.
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?