In other words, fat-specific insulin receptor knockout mice can eat a lot of “extra calories” and still hardly gain any fat mass."

I guess you missed this line in the article provided in the first link:

All four groups of mice gained weight....

A calorie isn't a calorie - low carbers have a thermogenic advantage.

"Thus, it is clear that insulin plays an important role in obesity, independent of energy intake."

And this in my response:

(btw I presume the insulin reactions among the groups were altered by the macrocomposition of the 4 diets, but this was not sufficient to prevent weight gain when excess calories are consumed)