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Originally Posted by Liz53
Wow, that is so interesting, Teaser, about the insulin being blocked and blood sugar rising - something I've never seen mentioned before. Hmmmm.....makes me wonder.
Can you summarize how the different sorts of stored fat might affect glucose levels - or cite some research? How can we anticipate how the fat we eat will be stored?
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I was gone for the weekend, my oldest nephew got baptized. No time to answer until now.
Last question first--I'm not sure. Generally, the fat storage will reflect the dietary fat, on a high-fat diet. On a diet that's low in fat, and high enough in carbohydrate that there's lots of fat being synthesized de novo, you'd end up with high levels of the sorts of fats that we synthesize. Mammals synthesize fatty acids in a certain order. First palmitic acid. Palmitic acid can be elongated to form other saturated fatty acids, the next in line after palmitic acid is stearic acid. Palmitic acid can also be desaturated to produce the monounsaturate palmitoleic acid, and stearic acid can be desaturated to oleic acid. This position of palmitic acid, as the first in line of the synthesized fatty acids in humans, might make sense of a special role of palmitic acid as a sort of molecular signal for a cell to switch between glucose and fatty acid metabolism. A cell might not start synthesizing fatty acids until it has taken in a certain amount of glucose.
They study essential fatty acid deficiencies in rats. The main model is a way of inducing the deficiency through a very low-fat diet and fasting. A relatively lean human's fat stores will last a month, or months. A lean rat's stores will last days, a week might be a stretch. If you suppose it's a week--fast the animal a full day, say it's run through 1/7th of its fat stores. The polyunsaturated levels will go down, there even seems to be a tendency for polyunsaturated fat to be oxidized as a percentage that's higher than their percentage in stores. During feeding, the animal makes the fats rats make--pretty much the ones we make, if overfed carbohydrate.
The process is slower in humans, because of a much longer half-life of our stored fats. The half-life can be shortened, through some form of accelerated fat-loss. I think this could probably be sort of hacked to speed up changes in fatty acid profile. If they could ever figure out what a desirable profile looked like.
Going back to the rats, instead of fasting them a day, and then making them replace the burned fats with synthesized fats, you could feed them cocoa butter, or some high-oleic acid fat like olive oil, on the fed days, and weight their fatty acid profile more strongly towards stearic acid and oleic acid. Or put in a little fish oil.
For palmitic acid-induced insulin resistance, I got that concept mostly from Peter at Hyperlipid, there are seven posts in his physiological insulin resistance series. And any number of posts that belong in that series, but are filed differently. I've never really dug right into the actual mechanism that Peter's talking about here, so until I've done a little more homework there, all I can do is point at his blog, and trust that Peter knows what he's talking about...
This post is one of those, the effect of butter vs. some other fats on insulin secretion. Peter wrote it when his ox (should that be milk-cow)? got gored when Dr. Davis suggested in a blog post that dairy fat had an insulin-stimulating effect. So by "blocks insulin" I guess Dr. Davis meant blocks its signal, not its secretion.
http://high-fat-nutrition.blogspot....nd%20Dr%20Davis
Any free fatty acid can compete with glucose for oxidation, if the free fatty acids reach a high enough level. Peter has a specific mechanism in mind for palmitic acid. There are two main issues to deal with here. One is the simple insulin resistance, the acute effect that Peter is talking about. The second is lipotoxicity, the damage done to cells, including beta cells, when free fatty acids and glucose are both elevated at the same time. I think oleic acid might have a role to play against both the benign short term glucose intolerance and the lipotoxic, evolving sort of insulin resistance.
It's the free fatty acids that compete with glucose, though--not the triglycerides. There are studies in pancreatic and liver cells, where the cells are exposed to either palmitic acid plus glucose, or palmitic acid plus oleic acid plus glucose. In the first case, various lipid products like ceramides, that are supposed to damage the cell, are produced in high quantities. The oleic acid prevents this--and seems to do this by increasing the synthesis of triglycerides. By lowering the free fatty acid levels in a cell, it makes sense that oleic acid should be capable of reducing not just ceramide formation and potentially long term damage of the cell, but also shorter-term physiological insulin resistance.
http://high-fat-nutrition.blogspot....tance%20%281%29
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I've been thinking about this for some time as my own FBG is usually five point something mmol/l whole blood. Converting my whole blood values to Mark's USA plasma values, this works out at about 100-120mg/dl. Normal to prediabetic in modern parlance. However my HbA1c is only 4.4%, well toward the lower end of normality and healthy. That's always assuming that I don't have some horrible problem resulting in very rapid red blood cell turnover. I don't think so...
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The general opinion in LC circles is that you need 150g of carbohydrate per day for three days before an oral glucose tolerance test.
I did this carb loading thing, then performed my own OGTT. It came out very normal except for mild reactive hypoglycaemia.
So, I often walk around with a fasting blood glucose of 5.9mmol/l and in mild ketosis, yet have normal pancreatic and muscle function, provided I carb load before the test. BTW my FBG dropped to 4.3mmol/l after three days of carb loading.
That then raises the question as to whether Mark "iwilsmar" and myself are typical of LC eating people, or an oddity or two.
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That's from the first in Peter's physiological insulin series. What Peter says here with the three days of carb feeding is something I meant to say in a more direct way here--
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One experiment I've been wanting to try, next time I buy some glucose strips is a carb-up. First a few meals with 50 grams of carb or so, to see what happens to my blood glucose--expecting awful numbers--and then two or three days of higher carbohydrate intake--250 grams+, like they say to do before trying to pass a glucose tolerance test, and see how my carb tolerance/morning blood glucose progresses.
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I typed it out a few times as a suggestion, but social anxiety got the better of me, and I retyped it as something I'd wanted to try myself (which is true, but no longer a direct suggestion). The 150 grams of carb a day is above the amount of carbs that coachjeff was eating, when he was on a moderate low-carb diet, as opposed to the more strict ketogenic diet he's eating now. Just because fasting morning blood glucose are elevated at a habitual carb intake of 70 grams a day, and even more-so at lower carbs, that doesn't mean anything is broken, and it doesn't mean that after three or four days of a higher carbohydrate intake, fasting morning blood glucose would go up, it could as easily go down.