I don't think there are any pathways via which fat can be converted into carbs--correct me if I'm mistaken--but fat makes your cells temporarily more insulin-resistant, so I suspect that's why you need more insulin when you eat fat. Even if you ate pure fat, it would temporarily reduce the efficacy of your basal insulin, and if you eat fat with carbs that require insulin, it reduces the efficacy of that insulin. If I'm right, how much to bolus for fat has a complicated relationship with not only how much fat you consume, but also how much bolus insulin you've injected to cover carbs and how much basal insulin you're using.
With 30 grams of carbs, and long-digesting ones at that, I'm surprised half the protein is getting converted into glucose. Whether and how much protein gets converted into glucose should be dependent on how much carb is present (carb being a more accessible source of carb for the body, and protein being valuable to the body as protein), though I have no idea what carb quantities affect protein metabolism in what ways.
It's hard for me to explore this in a really granular way in my own body because I still make a little buffer of endogenous insulin and I exhibit very little insulin resistance. But it's fascinating to think through the science and its real-world impact.
There are pathways to convert fat to glucose but they are very involved and inefficient. My belief is that fat in a meal enables greater availability of the carbs and protein by enabling better digestion. A wide range of nutrients are actually only fat soluble, not water soluble. Thus a non fat or low fat meal will result in poor absorption. This is why you should take most supplements with fat. In the same way I believe that fat helps absorption by enabling certain digestive pathways and slowing the rate of digestion.
Like Terry I count half the protein as carbs, but I don't bother with fat. We actually have a group here who follow a counting protocol called Total Available Glucose (TAG) which counts protein and fat. These ideas trace back to the "exchange system."
I don't understand all the ways that nutritional fat affects metabolism. At some point it starts to sail over my comprehension. I do know what dosing works for me. If fats add nothing to my insulin requirement, it could be that I'm absorbing closer to 58% of the protein grams and my "miscalculation" covers that error. As Bernstein says, what works, works.
It was my participation in the TAG group that I picked up and acted on this concept three years ago.
Agreed--whether it's more thorough digestion of carbs and/or temporary insulin resistance (almost certainly both) and/or some other factor--all that ultimately matters is what works. Which doesn't mean it's not interesting to try to understand what's going on, especially if you have my personality!
If you have a smart phone, download the app for Calorie King. I have found it very helpful. I also have a tiny book that I keep with names of restaurants and what I ate if it was a successful event BG wise, complete with the carb count. It saves time figuring out what I can eat the next time I go there.
