Start by increasing your intake of foods like fruits and vegetables, and decreasing your complex carbs and animal based protein. If you're not doing weights daily you don't need the high protein diet that many advocate. In fact at a certain point it's just being converted to fat. A few times a week with portions the size of your palm is adequate.
This is really hard because EVERYTHING has some sort of animal based protein in it, whether it's meat, eggs, fish or dairy. Especially if you're shopping for easy preparation meals or take out. So it means more preparation. For me milk in coffee is the big one, and a very overlooked factor in weight gain.
Your carbs, like protein, should be limited to occasionally but I don't advocate completely getting rid of either. Try get most of your carbs from fruit but if you're looking at complex carbs like rice, bread and potatoes than try swap to brown rice, whole wheat bread and sweet potatoes
Micro nutrient intake is also very overlooked compared to macronutrients, especially for general health, but I guess a lot of people look for an easy answer.
To come back to your question, filling your diet up with a lot more fruit and veg will fill you up way quicker. They simply take up more space in your stomach so you will get fuller quicker and for longer.
Obviously take away and pre packaged meals are mostly terrible for you. Loaded with hidden sugars and basically predesigned to make you fat and addicted to them
I've found this food score rating system to be a good way of identifying what I should be eating
https://www.drfuhrman.com/learn/lib...d-scores-rating-the-nutrient-density-of-foods
Edit: oh and lots of water