I'm a 5'6 dude weighing 165 lbs and my doctor has me on a 1200-1400 calorie a day diet. The 2000-2500 calorie per day diet is really inaccurate and only a rough average. I have some friends that eat over 3500 calories a day and can't keep weight on.You're only on 900 calories a day? That seems a little extreme