Fit-Day Issues

I've read other posts where people say that fit day totally overestimates the number of calories that they burn a day. I don't know if it's just be, but does anybody else think they have the opposite problem.

It's not like I'm dropping too much weight or anything, but if I go to close to 1000 under within a few days I'm completely starving for energy, and usually end up eating too much to compensate. I tried making it about 500 under (between 300 and 500), and even now I'm dragging, with an energy crash in the middle of the day and needing to mentally bully myself to get to the gym, or out the door for a run.

I drink a lot of water, and only have one cup of coffee a day, in the mornings, more for the taste than the caffeine at this point (should be switching to decaf soon). I do eat pretty regularly throughout the day, so I don't think it's crashing between meals, and I'm leaning seriously on Fit Day underestimating the calories I burn. Any ideas?