Everyone is saying counting calories, which is great, but I think it's important that someone new to it knows exactly how many calories is too much or too little. I find this tool great for calculating it:
http://www.choosemyplate.gov/myplate/index.aspx
I think if you're going for the healthy eating option, that tool is perfect since it breaks it down how much of each food group you need for a healthy diet. If you are going to keep eating whatever you so desire and just count the calories, and those foods can be considered junk food, then consider lowering the daily calorie intake by say...500 calories? But I'm no expert!
I eat 2200 calories a day of healthy food, it's a LOT and I feel stuffed. If I was eating 2200 calories of junk food, well then I wouldn't have lost any weight at all! So the point is, just make sure you do your research and try it out! Sometimes people feel too weak and sluggish on too little, some people don't see any weight loss on too many - sometimes it can just be trial and error.
Good luck!