when the "supersize me" movie was getting called out for being fake, a university professor dunked on the movie by just eating shit tier fast food on a caloric deficit and he lost weight.

your body is a biochemical battery. the macro type of calories is irrelevant to weight loss at the biological level. but you also have to consider that this is people, who have shit willpower. and shit foods don't provide much satiety, causing people to violate the deficit. if you literally only bought food to your deficit limits, you could eat the sloppiest trash diet.