It might be a less popular opinion for some, but to be honest, I'm not really into any type of diet.
You gain weight because you eat more than what you should, or/and because you choose less healthy foods, for example as you said, junk food. There is a more solid way for weight loss without sticking strictly to any type of diet - which can put pressure on you and make you fail sooner before you could reach your goal -. This particular one can be a little bit slower process depending on your body type, but less challenging.
The key is: Eat as much as you always should have do.
You don't have to leave behind every type of food you like. It's about paying attention to what you're eating, make your meals more consciously, and do not consume too much of those type of foods which contains too much calory, but have no proper nutritional value - like drinks with sugar, sweetmeats, chips etc. - , in other words, eat as much as you have to, keep your calory input in the same level where it originally should be - not less - and if you can, eat more times /day, but small meals. This will help your body to digesti faster and more efficiently and after a while, your stomach gets used to not taking in too much food, in this way you simply have no appetite for more.
It'll help you to lose weight, simply because you will not consume as much food as you did before, and if you are manage to insert any type of sport into your life, you can be sure that your weight loss will happen, without too much stress, which can actually make people to eat more and less healthy foods or crave for it, making the diet a living Hell.
No need to rush, so leave behind your strict expectations too. Losing weight slowly even better for your body and gives it time to adapt some way or another the small but constant weight loss. I'm telling this not because "I've heard that it worked to somebody and that somebody's friend too" but because it worked for me.
I've never really been "fat", but I definitely had some problem with my body and I wanted a kind of change. I gave chances to different type of diets, but I realized that I don't like these "rules", there has to be an another way, then I found it: just eat the way I should do before. In my case, it was more about the amount of coke and energy drink I consumed instead of food, but feeding my body properly and leaving unnecessary calories behind helped, I didn't consume less than I should, I consumed as much as I had to, from the beginning, and of the right food.
You even might be in the same boat like I am and this process can be faster than you'd expect. I lose weight easily, gain muscle much more faster than an avarage person, but as a con, I lose it very fast if I stop working out. Everything balanced, as all things should be. sniff-sniff
I also suggest to try to find a sport which is the most fitting to you, and which interests you the most, what you could enjoy. Not what is the most "effective". The most visible progress you'll reach is with the one you can do and willing to do. I prefer to do weight lifting and own-weight centered workouts. it helps me to drive out the accumulated energy I could not.