I'm doing a paper on de novo lipogenesis at the moment. So far, everything I've found says this isn't a major pathway. The results pretty steadily are 9 grams of fat a day synthesized in over feeding studies. Taubes says that "perhaps 30 percents of the carbs from anyone meal" are processed through de novo lipogenesis (387). I can't find anyone or anything to corroborate this. Can you guys? Am I missing something?
Here's a couple papers:
Update: Here's some more.
Found it. Or roughly it. Once they started tracking lipogenesis with isotope 2H20 for an extended period of time to account for the slow turn over rate of triglycerides (6 months), they found that DNL accounts for 20% of non-essential fatty acid or 10% of total fatty acid. This is in normal men aged 19 to 51 years, BMI 19 to 25. "No subject had a personal or familial history of diabetes or obesity or was taking any medication; all had a normal physical examination and normal plasma glucose and lipids concentrations."
This isn't quite the smoking gun proving that 30% carbs are thrown through DNL but it does prove that DNL is more active than thought in normal folk. Let's study up some diabetics and pre-diabetics soon.
Edit I had posted the link to the wrong study: http://ajpendo.physiology.org/cgi/content/abstract/286/4/E577?ijkey=3185355c16d68a660771e5087a09095b1afccd7d&keytype2=tf_ipsecsha:
The researchers themselves however minimize this difference. Interesting.
Taubes typically cites all his sources. YOu may need to get a copy of the book and find where in the book it says that in order to track down his citation. Anyway, Taubes is not infallible. Some of what he said will later turn out to be wrong, although I think his basic ideas overall will turn out to be reasonably accurate. I read your links above and in one of them it mentions that de novo lipogenesis rates are greatly increased in situations in which carb calories greatly exceed daily energy requirements and the person is gaining weight quickly (that was the second link), so it might be a case where this is more prevalent in those gaining weight. Also, some of this is a bit hard for me to understand, not being a bio major and all. But seems to me that it's unlikely that a large bunch of fat is both created and stored when we eat carbs. If that were to happen, then we would get fat very very quickly, not gradually. And there will be other factors. If the diet is already high in fat, then more fat may be less likely to be created. If the diet is low in carbs, much of a carb meal may go to glycogen replenishment instead of fat.
Of course, Taubes may have overstated the case and the carb prob may in fact turn out to be more of an issue of it supressing fat removal instead of creation of new fat. PLus, it only takes a tiny tip towards a tiny bit more fat stored each day to yield pounds and pounds gained year after year. I suspect whatever is discovered, it's really going to be just a subtle shift, a tiny imbalance for most of us, that results in a few more pounds every year, stubborn pounds that don't want to get lost, until slowly the metabolism gets more and more unbalanced.
If the body is making lots of fat from carbs, then it might also be using some of that fat right away and so not storing it? Not being a bio major, the science on some of these articles is a bit hard for me to follow. I don't think I am totally understanding what exactly they are measuring. In one, it seemed like they were only measuring stored fat that came from de novo lipogenesis. In another, it seemed they were only measuring hepatic fat generation but not de novo lipogenesis from other sources (like maybe fat cells) The third link froze my computer so I didn't read it.
If fat doesn't make you fat...? 9 Answers