BMR varies hugely by person, its not even a minor difference for some. Yes, calorie imbalance is a thing, but you can be a 300 lb person who eats 2750 calories

BMR varies hugely by person, its not even a minor difference for some. Yes, calorie imbalance is a thing, but you can be a 300 lb person who eats 2750 calories a day, also be a 200 lb person who eats 2750 calories a day, with each performing a similar amount of exercise. While calories in/calories out will help anyone lose weight, for some, even with the advantage of math - its still much harder, sometimes an order of magnitude harder. I've done this before, and I lose around 100 lbs, and I've kept off about 60 of it - but for the entire two years, I had a gnawing, burning pit of hunger whenever I was away. It never stops, and I never stopped being hungry. I just did my best to ignore it. On top of that, look how many social occasions revolve around food, to stick to any essentially effective diet requires refraining in those situations. That's even harder. "oh, everyone is going for fast food after the thing, I guess I can just have some water? okay, I guess that's okay" because one fast food meal exceeds your calorie goal for the entire day. Now you tell me, how easy is it to eat less if you never felt satiated, never stopped being hungry? My point here, is while calorie counting and exercise works, there is clearly more going on than just that.