Choose your insulin sensitivity well

People may or may not realise that I dislike meta-analysis. In the words of the great Malcolm Kendrick "One, two, skip a few, 99, one hundred". Or one of my uni lecturers, "The meta-analysis of dross is still dross". On a practical basis they just provide information overload to give a result determined by the selection criteria from which the individual results threads can be hard to extract.

So this is not one of my go-to type studies but, because it confirms my biases, I'll cite it here

Effects of Saturated Fat, Polyunsaturated Fat, Monounsaturated Fat, and Carbohydrate on Glucose-Insulin Homeostasis: A Systematic Review and Meta-analysis of Randomised Controlled Feeding Trials

which came up on a twitter feed of Tucker's.

The study looked at isocaloric replacement of 5% of carbohydrate calories with various fats or changing the number of double bonds in 5% of calories using various fatty acid substitutions under controlled conditions.

The important result of this data trawl is this, extracted here from Table 2

I think it is quite clear that particularly replacing saturated fat with PUFA (mostly linoleic acid) decreases insulin resistance. The more double bonds added, the greater the insulin resistance reduction.

That's good, right? We all want to be insulin sensitive, right?

So if I give you these HOMA scores, from a different study, which of the groups would you like to belong to?

Before you choose you might want to ask what the difference is between the groups. This is the original table from

Insulin sensitivity is increased and fat oxidation after a high-fat meal is reduced in normal-weight healthy men with strong familial predisposition to overweight

which I've mentioned previously.

OK. Choose your parents wisely.

Statistically, if both of your parents are obese, you are in a bad place for staying slim. You are very likely to be MORE insulin sensitive (p less than 0.05) than your luckier mates with skinny parents. Personally I think genes have very little to do with obesity. Learning your food habits at your parents' knee has a very much larger influence on your future waistline.

How much linoleic acid to you have to add to your diet to lower your HOMA-IR score from 1.6 (ie normal) down to 1.1 (going to end up like your overweight parents)?

I don't know for a human but for a mouse it's generally enough to increase LA from around 4% of calories to something over 6% of calories that gets the job done.

Any hypothesis of obesity has to be able to account for the above data. EBM or CIM.

Peter