I'm not sure that there is much if any processed food still in my diet (maybe just the English muffin in the morning?). I stopped buying/drinking soda pop decades ago (a low-hanging fruit indeed — I lost almost 10 pounds within a month of making that dietary change alone).
And since I have tried little things like switching to peanut butter that contains only peanuts (no salt, no sugar, not palm oil — sure, I have to stir it when I open it for the first time). I've moved to whole grain bread. Other small changes like that I can't remember right now.
I still have a BMI that's too high.
The only time I have significantly lost weight was when I was prepping for intestinal surgery nearly a decade ago. I was at the time worried that eating too much would literally kill me (I was worried about bursting my intestine) that I ate very small portions for each meal.
I'm not sure why I can't change my habits such that I continue to eat those small portions (now that the fear is gone).
That diet isn't going to have the same effect for most people, but in my case it significantly lowered my inflammation and general discomfort, which led me to lose 90lbs with no actual effort on my part.
I knew one dude who was always hungry and it turned out he just desperately needed B12. Now he snacks on B12 gummies and feels much better. Debugging our bodies is more complicated than debugging a software program, but no programmer would say "Just run the program less!" if someone complained a program was eating up all the CPU.
The one thing that is always good for humans, whether we lose weight or not, is some physical activity. Whatever we can enjoy enough to do regularly, without injury, is a great choice.
I wish the medical profession would stop focusing on diet, when it doesn't understand it and calorie restrictive diets are one of two lifestyle components we know actually do contribute to obesity.
That is not what any of the studies I have read find, particularly not past the short term: past calorie restriction diets is one of the factors associated with developing obesity.