How to loose weight at 44?

I am 5'5 and I weigh more then I ever have in my life. I weigh 205 lbs. I have tried every diet that is out there. I have taken every kind of weight loss pill that is sold over the counter only to no avail. I need to know what can I do to boost my metabolism? I do not over eat. This is the thing I don't understand is why am I gaining weight when I don't eat over 1200 calories a day. I very seldom eat bad starches. Please, if someone can help me, please help.