Well, that is obviously the wrong idea. Even basic logic speaks against it: people lose weight on keto diet, people lose weight on vegan diet... so neither protein, fat nor carbs can be causing obesity. But what do foods that we know are obesogenic have in common? 1) They are highly processed and/or 2) they combine fats and carbs into single package.
But it is true that we don't know for certain. What we do know is that this dietary experiment we have had going since 1970s at the latest has failed completely. As I tend to say: paleo diet should be the basis of any diet, and then you further adjust it based on how your body responds.