The short answer, is I would agree. Anytime we look at causation, it gets hard. Do we really ever know the cause? We do know how close events are to each other via association. I like association instead of causation, but I understand your point. The hard part is it's not ONLY insulin and the tissue sensitivity to insulin can vary a lot AND be different in different tissue (liver, vs muscle, vs fat are the big ones). If you have a particular study. I may be able to give you a better answer. If we look at Type 2 Diabetics, they can still lose weight, even with goofy insulin/glucose values; but it probably won't be as easy as someone who is more healthy. Rarely, is it ever ONE thing 100% of the time in physiology. The key is to try to narrow it down to the things that 1) matter 2) we have some control over; and for that, endogenous insulin fits nicely. Hope that helps! Rock on Mike T Nelson PhD(c)