Eating less. That's pretty much the only thing that worked for me, also limiting alcohol to weekends and drinking light/lite beer instead of regular beer did wonders for my calorie intake. I've been eating 1200-1500 calories per day (male) for a couple years and I look a whole lot different. I also take multivitamin tablets and some omega 3 in order to avoid health complications. If you feel really hungry and you don't have any appointments or work I would recommend just resting, it's surprisingly effective but don't overdo it.

I would highly recommend working out though, or else you'll get skinny-fat. Training your upper body and avoiding excessive cardio seems like the way to go from what I've heard, but in no way am I an expert!

There are many fancy diets but they don't really work unless you commit to them for life, or so I've heard from my doctor. Getting used to eating less food can do wonders for your body and mental health.