First of all there's a huge gap between home made hamburger and, well, anything else tbh. Actually, let's expand it, there's a huge difference between home made anything and any other kind of food, be it restaurant or assembly line made.

Backing up a little though, if you make a hamburger at home, with lean good quality beef that you grind up yourself or ask them to grind it for you at the counter, lots of veggies and very little oil, on a home made bun or on actual bread (the kind made with flour, water and salt, that's it), then it's quite healthy. Still wouldn't eat it more than once a week since red meat yada-yada, but still, not that bad.

What you get at a fast food though is very low quality meat with lots of fats, dipped in other fats, sugar and spices to mask the flavor, processed bread, processed cheese, very little veggies and, usually, a side of french fries and a soda, which are a meal onto themselves. Let's take McDonald's, looking at their website a quarter pounder is 500+ kCal, the medium fries are 300+ kCal and a medium coke is 200+ kCal. That's 1000+ kCal for a "meal" full of fats, sugar and processed food. Also it's a huge spike in insuline which will lead you to a huge crash just a few hours later leaving you hungry and craving for more.

Restaurants are also a bit guilty of this. They tend to add much more fats than you'd ever do at home in order to drastically improve the flavor of their dishes. Can't even fault them for it, if I wanted a bland healthy meal, I'd have eaten at home. If I'm going to the restaurant it's because I want a great tasting dish. Ready made meals you can get at a supermarket are also full of fats, vegetable oils and preservatives in order to mask the shitty flavor.

So at the end of the day I'd say the best thing is to avoid as much as possible processed foods, avoid all take outs and deliveries, go out to eat maximum once a week and cook all your meals yourself starting with simple ingredients. It's not that hard either and cooking can be fun.