Innumeracy In The Medical Community

Sigh. Dr. Davis recently blogged ostensible evidence that butter has an "unusual ability to provoke insulin responses", which will trigger weight gain, "because of butter's insulin-triggering effect, doubling or tripling insulin responses (postprandial area-under-the-curve)."

Doubling or tripling post-prandial insulin AUC? OK, I'm intrigued. So I read the study.

The insulin AUC numbers from the study are as follows

19960 +- 2766 control*

27970 +- 2107 VEFO
29619 +- 4975 MUFA
34749 +- 1167 HPSO
37582 +- 4364 SFA (butter!)

*And here's a really important detail: the "control" meal has no fat at all, and is not isocaloric with the test meals. "the macronutrient profile was as follows: 72% fat, 22% carbohydrate, and 6% protein (see Table S1 under "Supplemental data" in the online issue). The subjects also consumed the same test meal containing no fat as a control meal". So the butter test meal has nearly 4x as many calories as the control meal. The AUC for insulin between the two is about double for the butter, but that seems like a useless measure.

Comparing like-for-like, the spread between average insulin AUC for butter meal and the isocaloric alternate fat meals shows the butter to be about 34% higher than VEFO and only 8% higher than HPSO.

8% above the nearest non-butter meal is not "doubling or tripling".


P.S. A few further notes.
(1) Quick search of pubmed turns up a few interesting things: one, papers contradicting this study, when isocaloric meals were tested (but seems like potatoes are a popular choice for carbs instead of wheat flour used by Dr. Davis's cited study). Here's an example: "Differential effect of unsaturated oils and butter on blood glucose and insulin response to carbohydrate in normal volunteers"
(2) Studies like this all seem to be studying responses of fat + carbs. Not sure how relevant this is if you don't eat a lot of carbs.


P.P.S. Peter at Hyperlipid has a more thorough piece on this, in his typical hilarious-yet-rigorous style ("FFAs do not pop in to existence merely to prove that butter is going to kills us through obesity")