While cutting calories is important when losing weight, exercise is just as, if not more important than cutting calories. And 800 calories is almost too little calories. The more active you are, the better your body will process what's been put into it. Trust me, I've lost half of what I used to weigh through getting active and cutting about 300 calories a day from my diet. And...if you loose too much weight too fast, you'll have loose flesh that won't tighten back up. When it comes to weight loss, slow and steady wins the race.