Take a deep breath. you didn t get heavy in one week, nor are you going to get fit in a short period of time. Set realistic goals (1-2 lbs of bodyfat lost per week). Eat n amount of calories you can live with without binging (12-14 times your weight in calories per day). Break your calories into six smaller meals per day. Drink plenty of water. Do some exercise. At this point it does not matter what you do, just get your body in motion and it will respond. When you drop 10-15 lbs (if you are truly fat and not some neurotic teenage girl that thinks being 10 lbs over what some website says is perfect is fat) you can start some resistance training with weights and/or things like pushups and reverse crunches.