Actually it helps a lot in steering them away from complex bullshit that generates decision paralysis. I you read books about the latest diet fad or take a course, or buy weight loss products, you are actually consuming a lot of energy and willpower that you could use in simple lifestyle changes like "first step drop all junk food and sugar".
It just comes off as pedantic/dumb well-actually-ism.
Yeah, fat people know about calories in/calories out. That in itself doesn't make them slimmer.