I understand what you're saying, and I agree in essence, but you're still making it sound a lot easier than it is. It can be an extremely difficult process from a psychological perspective. Many people who are obese got there from habits and behavior learned as a child. Some have associations with eating that are so ingrained that it's almost a part of their personality. The worst part, I think, is the viciousness of the emotion cycle, where you need to be motivated and confident to make a real effort at change, yet being overweight can leave you feeling depressed and lethargic.
There is also the financial state many people find themselves in, where the cost of fruits take them off the table and the most economical route is empty carbs. The quality of my own diet has plummeted since I lost my job, so that's one factor I can understand wholeheartedly.
There are other influences that can creep in, as well. Job situations where a person is on their feet all day and the last thing they want to do is exercise, situations where no healthy foods are in easy access, too many enablers chipping away at a person's resolve, and I'm sure there are more.
Enablers are a big part of the reason I had a slow weight gain over several years. True story, no lie, I used to have an employee, a sweet older lady, who would bring me a snack and a soda whenever we were scheduled to work together, or even if one of us relieved the other. It grew until she was bringing me a Little Debbie Star Crunch cake and two sodas, then maybe some miscellaneous candy. I eventually hinted that I was trying to eat healthier and it seemed like she got it. The next day she brought me a Little Debbie Zebra Cake, instead; she thought it would be better because it had less chocolate. My mother wasn't that bad, but she would bake a lot of sweets and bring me a slice, always with the "a little bit won't hurt" mentality. I really had to get firm with both of them, and even say "no, take it back" a few times.
I lost the weight I gained, but it was a hard struggle, not just with myself, but with other people.
I have a friend and former coworker who just gave up. I don't think he'll ever lose weight until he ends up in the hospital. Eating is a psychological addiction for him. If he can't eat when he's stressed or bored then he can't think, he becomes irritable and unfocused. It's literally a waste of time to talk to him if he's thinking about food. He's been on hundreds of diets and he always fails, which crushes his spirit. His entire family is overweight, his wife is overweight, and food dominate his life. He was raised on Mountain Dew and drinks 8+ cans a day despite being a diabetic.
So, no, it's not easy by any means.
The only way to stop the obesity epidemic, I think, is to target children now, get parents to understand how important it is to give their kids good food, that they're essentially killing them if they raise them on junk. We have to change the culture as much as we can. If you want a person to be honest then you teach them that from childhood. If you want a person to be healthy then you teach them that from childhood.