After-eating effects: Carbohydrates vs. fats

25. November 2009 William Davis (17)
In the ongoing debate over whether it's fat or carbohydrate restriction that leads to weight loss and health, here's another study from the Oxford group examining the postprandial (after-eating) effects of a low-fat vs. low-carbohydrate diet. (Roberts R et al, 2008; full-text here.)

High-carbohydrate was defined as 15% protein; 10% fat; 75% carbohydrate (by calories), with starch:sugar 70:30.

High-fat was defined as 15% protein; 40% fat; 45% carbohydrate, with starch:sugar 70:30. (Yes, I know. By our standards, the "high-fat" diet was moderate-fat, moderate-carbohydrate--too high in carbohydrates.)

Blood was drawn over 6 hours following the test meal.




Roberts R et al. Am J Clin Nutr 2008

The upper left graph is the one of interest. Note that, after the high-carbohydrate diet (solid circles), triglyceride levels are twice that occurring after the high-fat diet (open circles). Triglycerides are a surrogate for chylomicron and VLDL postprandial lipoproteins; thus, after the high-carbohydrate diet, postprandial particles are present at much higher levels than after the high-fat diet. (It would have been interesting to have seen a true low-carbohydrate diet for comparison.) Also note that, not only are triglyceride levels higher after high-carbohydrate intake, but they remain sustained at the 6-hour mark, unlike the sharper decline after high-fat.

It's counterintuitive: Postprandial lipoproteins, you'd think, would be plentiful after ingesting a large quantity of fat, since fat must be absorbed via chylomicrons into the bloodstream. But it's carbohydrates (and obesity, a huge effect; more on that in future) that figure most prominently in determining the pattern and magnitude of postprandial triglycerides and lipoproteins. Much of this effect develops by way of de novo lipogenesis, the generation of new lipoproteins like VLDL after carbohydrate ingestion.

We also see this in our Track Your Plaque experience. Rather than formal postprandial meal-testing, we use intermediate-density lipoprotein (IDL) as our surrogate for postprandial measures. A low-carbohydrate diet reduces IDL dramatically, as do omega-3 fatty acids from fish oil.
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Comments (17) -

  • darnoconrad

    11/25/2009 3:19:52 PM |

    The Graphs are too small to read even when clicked on.

  • Robert McLeod

    11/25/2009 5:31:22 PM |

    It's not solely the fault of de novo lipogenesis, as even on a high fructose meal with radio-nucleotide labeled carbon in the fructose, only like 20 % of the triglycerides in the blood are from DNL.  Glucose consumption doesn't seem to result in DNL unless the liver is already full of glycogen.

    Insulin is known to down-regulate acylation stimulating peptide (ASP), which is the paracrine hormone that regulates uptake of lipoprotein (i.e. "cholesterol") micelles into fat cells.

  • Ms. X

    11/25/2009 5:46:34 PM |

    Dr. Mike Eades wrote a while back that fats, especially saturated fats go into the lymph system after digestion, and not immediately into the bloodstream.

    Why is it then that "since fat must be absorbed via chylomicrons into the bloodstream" is an "accepted" notion?  You implied it was wrong, without actually saying so...Do most medical practioners really not know how fat is absorbed into the body?

  • DrStrange

    11/25/2009 8:02:26 PM |

    You MUST look at this in context!  Excess dietary fat, especially saturated fat, causes insulin resistance.  It takes about 2 weeks of consistently eating approx 10% calories from fat, not more and not cheating, to remove that huge component of insulin resistance.  If the study were done in that context the results would be quite different.  How do I know?  I have done it several times on myself!!!

  • DrStrange

    11/25/2009 8:03:30 PM |

    oops, forget to request email follow-ups. So now I have.

  • TedHutchinson

    11/25/2009 10:42:41 PM |

    @ darnoconrad
    Dr Davis did say "full-text here hoping people would follow the link, download the PDF, and have their own copy to enlarge as required.

  • Stephan

    11/25/2009 10:42:41 PM |

    Hi Dr. Davis,

    Thanks for posting this.  It answered a question I've had for a while now.  The palmitate is interesting as well.

  • Helen

    11/26/2009 2:18:06 AM |

    Very interesting and kind of scary, with family members of mine with heart disease pounding down the carbs and cutting the fat.  

    I'm a bit confused by the Track Your Plaque Program, though.  In some of the info on the main site, saturated fats are described as inflammatory and something to be avoided.  But you seem to consider them okay - am I right?  And Dr. B G at AnimalPharm, who says she is counseling her clients with the TYP program, is big on saturated fats.  Can you explain the discrepancy?

  • Dr. William Davis

    11/26/2009 2:38:08 AM |

    Hi, Helen--

    The Track Your Plaque program stand on a number of issues, including saturated fat, has evolved over the years. We now do not restrict them, but nor do we suggest a carte blanche  approach, since we do continue to maintain rather strict LDL targets for plaque reversal.

    I believe that Dr. BG was expressing her own opinion in the Animal Pharm blog. While she's got plenty of great thoughts on this issue, it does not represent the "official" stand of the program.

  • Nigel Kinbrum BSc(Hons)Eng

    11/26/2009 9:18:52 AM |

    Is it possible that the higher fat diet hit an optimum fat/carb mixture, where carbs were low enough to keep fasting TGs low and fats weren't high enough to spike post-prandial TGs?

  • Dr. William Davis

    11/26/2009 2:51:39 PM |

    Hi, Nigel--

    Good question. Stay tuned--plenty more on this conversation to come.

    The entire world of postprandial metabolism is truly a fascinating, though complex area, that is only beginning to yield to investigation. The Oxford group has made enormous contributions to this understanding.

  • Anonymous

    11/27/2009 10:00:20 PM |

    Thanks for this, Gretchen, that's a lot of work!

    It's interesting that my husband's endocrinologist, whom he is seeing for high blood pressure, insists on non-fasting labs.  He has my husband get his tests (blood and urine) one hour after a meal.  He says the fasting tests are very misleading.

  • Helen

    11/28/2009 2:34:27 AM |

    Another question on saturated fats.  I know they raise LDL, and lately I've been reading that they raise the benign kind, not the vLDL.  But I have read in many places (including the Track Your Plaque article I mentioned) that they are "inflammatory."

    Is that a false accusation, confusing saturated fats with trans-fats (since hydrogenated fats were used in some experiments regarding saturated fats)?

    Or is it one of those things that depends - on other dietary factors or disease states, such as diabetes, etc.?  Or is it unknown?

    It's hard for me to believe that nature would only want us to eat monounsaturated and omega-3 fats (as omega-6's are inflammatory, too).  That would seem fairly limiting for an omnivore.  Of course, it could be a proportion thing, too.

  • StephenB

    11/30/2009 7:32:50 PM |

    Helen wrote:
    "Another question on saturated fats. I know they raise LDL"

    The above may not be true. There may be a small near term rise, but long term I don't believe they have no impact or even lower LDL. You might find this blog entry interesting.

  • Anonymous

    1/16/2010 1:25:20 PM |

    Rather interesting site you've got here. Thank you for it. I like such themes and anything that is connected to this matter. BTW, try to add some images Smile.

  • buy jeans

    11/3/2010 3:48:57 PM |

    It's counterintuitive: Postprandial lipoproteins, you'd think, would be plentiful after ingesting a large quantity of fat, since fat must be absorbed via chylomicrons into the bloodstream. But it's carbohydrates (and obesity, a huge effect; more on that in future) that figure most prominently in determining the pattern and magnitude of postprandial triglycerides and lipoproteins. Much of this effect develops by way of de novo lipogenesis, the generation of new lipoproteins like VLDL after carbohydrate ingestion.

  • simvastatin

    5/25/2011 5:22:39 PM |

    Consequently, one of the advantages of glucose and other carbohydrates is that they can enter into the oxidation process much more quickly and provide energy more rapidly.

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