It's much like the scientists working in every field imaginable that get grants to study the obvious; if you eat too much and don't exercise enough, you get fat. I knew that even BEFORE I started diet counseling with my Dr. Even looooong before the internet.
This totally ignores the genetic component of obesity, phenotypic plasticity, and development. The statement that it's all about energy balance and we know all there is to know is simplistic and trite.
That scientists get grants to study the obvious is a straw man. Have you ever read a grant proposal? Are you an expert in every field imaginable? There are many things people once thought were obvious (e.g., the earth is flat, ulcers are caused by stress) that are not. But science bashing is fashionable among the luddites of the world so blather on. You have a computer and that's all that is required to be an internet authority.