We're agreeing more than we disagree at this point. I'm with you on most of what you just said. Lemme just show you were I'm at:
"Most of the fat people are eating more calories then they need"--agree. You're correct here and I can't argue with that.
"even if they go to gym it wont change their weight"--disagree. Regular exercise will reduce stored body fat. Even if they stay the same weight, they'll be gaining muscle and losing fat.
"of course not over eating + exercise will be better than just not over eating"--of course.
"eating slightly less calories than you need you will lose weight 100%."-- you would be amazed at how ineffective and inefficient(considering the will power+effort required) this is. Yes, you can lose weight through diet alone. If we're talking about permanent weight loss, and not just fasting/cutting, this shit is so bad compared to your other options that it's not worth considering or recommending.
Seriously, I get where you're coming from. I used to think like you when I was a bit younger and took my metabolism for granted. I thought it was simple. It's really not; and the more you get into it, the more you find that out for yourself. I thought I was thin because I was doing something right, and people who weren't were doing it wrong. In some cases, sure, people do overeat; but if you consider all factors, I was giving myself undeserved credit. It took my body type changing to "skinny-fat" without me making any lifestyle changes for me to realise I was not living/eating/exercising as well as I had thought. It took me a lot of research, as well as learning from people who actually know their shit(trainers and nutritionists), for me to realise I didn't know anything(and what I thought I did know was wrong). I eat healthy(healthier at least) now, and work out twice every day, and barely drink alcohol, and there are still a million things I need to improve on and learn and correct. Shit is a life-long journey. It is not as simple as "don't eat doritos"(although that is good advise). Idk man, I just have a sore spot for seeing people give incorrect or incomplete health advise because I see a younger and more arrogant+ignorant version of myself in those people. If you want to see what I'm talking about try losing 5 pounds with diet alone. Just 5, sounds easy, right? Don't cheat by taking a shit before your second weigh-in lol. I guarantee that it will fucking terrify you.