The reasons are several. I think the biggest reason is that patients are not used to an extended period of inactivity. In other words if it takes you 2 weeks (14days) to heal from a tummy tuck, that certainly doesnt mean your going to the gym on day 15.It also shouldnt mean that your eating pizza on day two either. its important to remember that a gradual return to excercise begins with light aerobic work outs over a longer period of time and that maintaining a well balanced diet during this time is just as important. We all want the "quick fix". We want to lose weight now, and look fit now. We need to understand that in most cases this is a gradual process. During the postop recuperative phases, eating right and maintaining a nonstrenous level of activity are important in the healing process. Water weight is present after surgery . Calories are burning faster after surgery with increased metabolic demand for wound healing. These issues actually cause one to lose weight. So in essence there is a fight to reach an equilibrium after surgey. It is a gradual process which is encouraged by consideration of these issues