Eat 1/3 of calories from protein (improves immune system, improves healing rate & mood, your blood has amino acid levels like sugar, respect them). Substitute simple sugars (2-10% thermogenic calorie loss in digestion which also correlates to low prebiotic value) for complex carbs (~30%). Eat more fiber. Just buy some dextrin it's a lot cheaper than produce.
Eat potassium (spinach, cabbage, potatoes, milk, oranges, NOT bananas you'd need 12 daily) and iodine and a multivitamin (lacks both in USA) so you stop feeling a weird craving for food that never can be satisfied.
former fatty here with a little addition: Also just eat less outside of your meals. Go diet in the supermarket by buying less, instead of dieting by not eating what have at home. You spend 20 minutes in the supermarket and multiple hours at home. It's MUCH easier to be strong for 20 minutes than for 12 hours.
That's basically all there is to it if you're not trying to get a six pack. It takes some time to get used to, but then your body will start figuring out things by itself (like '"I need more vitamins" and "I hate feeling bloated because of empty calories").
It isn't only eating disorders either, there are so many conditions (and medications!) that can cause or have the side effect of weight gain, and then a ton more that don't directly cause it but do directly make it hard or even impossible to "work" off.
And you can't just say no, it's a systemic problem that could be solved with walkable cities, better public transportation, stretching breaks at work, eliminating or greatly reducing subsidies for corn and processed foods, and other stuff. We have to consider every step food takes from its source to the shelves, and all the reasons citizens aren't able to be more active or afford foods that could better support an active life.
All things that are certainly achievable if we all take responsibility for community health instead of wailing on individuals.