Fine, but the thing is that some people, a LARGE number actually, Have No Choice! 'Food deserts' are real! People surrounded with no way to 'eat right'. Kids mercilessly advertised to demand HFCS laced 'food' and drinks. Sunny-D should be labeled toxic! It's total crap! How many 'fruit juice' containers announce 0% fruit juice? Or way less than 99%.
The crap that is out there that people are almost literally forced to eat is heartless, cruel. No wonder the world is getting fatter, AND 'American food' is sold around the world, and is often made dramatically more healthful in countries that require it. People carp about the EU, but they are putting the screw to the corporations pushing diet busting crap on people in their countries. It's real... America has a 'food' problem. It's more a delivery system for diabetes and obesity, and too many people have no choice.
As the other poster mentioned, the main thing is the calories. So if for some reason you're being forced to eat fast food for every meal, then you need to look up how many calories you need (based on your age, height, current weight, and activity level) to either maintain your current weight or lose weight (if needed) and stick to that. I actually use what they call a "zig-zag" calorie plan to maintain my weight. Here's the calculator I use:
Calorie Calculator - Daily Caloric Needs

Hint: if you're using up your entire daily calories on one fast food meal (which is easy to do if you don't count calories), you're going to have trouble!