I spent a couple years of nothing but eating out and drinking lots of beer. Then the health problems started rolling in and I had to take corrective action.
I went from 320 back down to 175 in a year.
I counted calories, quit soda, quit beer, dropped candy like foods, and started counting calories. I gradually worked from about 3,000 calories down to about 1,800. Once I dropped my weight down to about 240 I started working out hard core, too.
You do not want to get below 1,800. You'll have hair loss, malnutrition, lose muscle tone, and have blood acidosis.
But you do have to count ever last calorie, including the ketchup or bbq sauce you put on your meat. It will work, trust me.