The nuance here is all in the difficulty of actually taking in fewer calories, due to things like limited willpower
As a kid i was always told to finish my plate, then the usual "think of the starving kids" guilt trips, and whatever else.
As an adult, I just eat smaller portions of the same garbage I ate before, and I started to lose a bit of weight. I didn't change anything else (at the time).
Now I'm working on the rest, but the biggest stepping stone for me was literally just eating smaller portions.