No, I didn’t have any tests done.
I suspect that in some cases of insulin resistance it’s not that sugar is a problem as much as it is that sugar metabolism is dysfunctional. There is some evidence that elevated free fatty acids in the blood may be the cause of that. Presumably you have elevated levels of free fatty acids if you’ve been diagnosed with metabolic syndrome. Is that true? Have you had the free fatty acids analyzed? It would be useful to know if they are high omega 6. My pet theory is that elevated omega 6 free fatty acids may be at play when glucose metabolism isn’t working. Trans fatty acids are also a possibility.
How long have you had trouble eating enough calories? What do you eat now? What did you eat prior to digestive problems? Presumably if you’re not eating enough then you’re burning stored fat. What were you eating before that started happening? How lean were you then?
I’m curious if you might have a lot of stored omega 6 or trans fats getting released into the blood and overwhelming insulin sensitivity. Or maybe you have a lot of omega 6 or trans fat in your diet. That’s just one possibility.