i thought the whole point of a post-workout shake was to shuttle nutrients away to the muscle. and, as you say, fat slows this down rendering the pwo shake useless. Also, i don't use dextrose, i use oatmeal as do many on this board. Furthermore, I don't know much about diabetes, but i imagine that you wouldn't have trouble incorporating them into your pwo shake-minus the fat.
Sure that is the intended purpose of pwo nutrition but it seems that many people get this confused with triggering a large insulin response. Exercise temporarily improves insulin sensitivity - meaning that nutrient uptake under 'normal' insulin levels is increased. How high of insulin levels does one actually need to restore muscles?
Something that I have never seen numbers on is how much and how fast the body can shuttle nutrients to (depleted) muscle. Glucose (aka dextrose) is absorbed extremely fast; I question how much of the 80-100g dosages that many ppl use goes to fat storage vs lean tissues. Of course lean body mass, level of depletion, and previous meals would be factors.
Adding in fat would not necessarily make the said shake useless; is the overall rate of digestion/absorption that is important. Take the oatmeal for instance, on the GI scale it is about half of glucose. One could add in fat to a glucose shake and achieve an overall GI on par with oatmeal.
Anyhow my point was that I think it's possible that the big glucose shakes are possibly overkill.
FWIW when I'm dieting I do use about 15g of oatmeal in a pwo shake (150lbs @ 8-10%) but when I'm trying to build my priority is
minimizing insulin levels while maintaining positive energy balance.