I linked that paper because it was about the mechanism, but there’s definitely papers going around where study participants ate the same excessive diet (and carbs) where the intervention group ate whey protein too or something to that effect and lost visceral fat

I wouldn’t be surprised if improving protein intake or resolving some specific amino acid imbalance (relative to each other or carb intake, given some amino acids can be created from carbs) or deficiency improves insulin sensitivity and glycemic control