It's a stereotypical misconception, IMO.
People can eat either diet (follow either lifestyle, smoking etc) and still get fat or lean...eating too much good food (above needs*) and doing no exercise will still result in gaining weight, just as eating a less than optimal or junk food based diet can also lead to remaining lean if the calories are enither in excess and exericse is added in to the mix.
Food, above needs, it's interesting how the leaner person tends, overall, to eat more than some of the bigger/fatter people, another misconception that if a person is bigger then they are that way because they're eating too much yet they are eating possibly less than someone who works out and appears leaner.
It's more complex than diet alone.
36.5 kg /80.3 lb Middle-Finger DL (right hand)...