There's so much conflicting information; on this thread, online, and out there in general.
So, lets hit the big issues. First off, you might want to visit your doctor to have him check you out. You are very over weight so there might be a good reason to make sure your heart is able for it.
There's also the fairly major issue that most studies show that fat people are fat for life. Simple as that. Because for the most part, your body is a reflection of WHO you are not WHAT you do. We understand that these things are both linked but if you are not disciplined, focused, hard working and use those elements in a prioritized body image, you'll just yo-yo back and forth. We all have the fat friends of facebook who post "Super workout at the gym, time for a treat", etc.
So, if you are over weight there are some things you need to do. First off, forget about exercise and working out. Unless you fundamentally enjoy it (which, as an overweight person you probably don't or you wouldn't have become overweight) it's just going to make getting yoru diet sorted out. Seriously. Your blood sugar levels will yo-yo, you'll think you've earned a treat, your schedules and shit will be fucked and you'll end up cheating your diet. So, if you are serious about weight loss, health, and not dying, then you need to put EVERYTHING into diet (for now, at least).
Diet is fairly obvious. Drink water. Cut out sugar. Eat less shit. Reeducate yourself as to what is good and what is bad. If you are fat and lazy you wont bother, and well that just proves what I said about it being WHO you are not what you do. But here's a pro tip ... if it comes in a packet you don't eat it. That might be really hard for you, so just work off %s. This week reduce the number of meals you at where stuff came in a packet. And keep going.
Ultimate goal, but not something most people can ever do is to eat only fresh fruit, meat and vegetables. But most people will never get there.
Once your diet is sorted, once it is a habit, you'll be loosing loads of weight, but only then can you start to exercise. Only when exercise won't be the reason to disrupt your diet can you start to train.