800 calories a day and 1 hour of real exercise would definitely result in 5 to 10 lbs lost for me that week.  I'm pretty sure I couldn't maintain my other normal activity.  According to the meter on my stationary bike, I can burn over 800 calories in less than 30 minutes.  No way she is actually maintaining those numbers for even two days.  I bet her workouts involve 2 mph walks for 31 minutes which she rounds to the nearest hour.  I bet she counts that 2 liter of Coke as a can of diet Coke because she's on a diet afterall.