Calories in calories out!
I love this app!!! I travel all over the world (a lot) and this works for me so far.
Set your RDI to lose weight and stick to it! You can eat anything you want, just don't go over your RDI! Exercise at least 30 min. per day if you want to speed things up and get over occasional slumps.
Based on the advice of a dietitian I set my RDI about 500 calories lower than the recommended FatSecret RDI.
You should loose a steady 1 - 2lbs per week. If you start loosing more than that, bump up your RDI.