DR. ANDREAS EENFELDT, Swedish doctor and low-carb blogger :
Certainly there seems to be some insulin response to dairy, possibly due to the milk protein (and of course the lactose). That said, I hardly think butter is making anybody fat. Milk (and possibly cream and cheese) can be a problem for very sensitive individuals though, as they contains more lactose (milk sugar) and milk protein.
Saying butter can triple insulin levels is only true relative to starvation levels. In the López study, insulin got only marginally higher with butter than with isocaloric meals containing different fats: about 205 pmol/L compared to average about 165 with other fats. Thats about 25% higher, not 200% higher (“tripled”). Additionally there is a lot of statistical uncertainty in those numbers. Plus, butter contains some carbs and protein, the oils do not. So we shouldn’t be surprised that the insulin levels got a bit higher after the butter meal.
If you instead substitute bread for the butter, calorie for calorie, the insulin levels would shoot through the roof. In other words, if eating more butter makes you eat less bread, that will surely make you thinner, not fat. That seems to be the way it works for me and my patients. I eat more butter than ever, more than most people, and I am as thin at 38 as when I was 20.