To the best of my knowledge it is not possible to lose fat in just one specific area. I am no expert in this field, but I believe the difference you are seeing is because there are two different types of fat at play here. The first is subcutaneous fat, it is located between the skin and muscle tissue all over your body. This is the fat that is measured when you have your body fat checked with a set of calibers. The second type is visceral fat, it is located around your internal organs, to include your intestines. It kind of acts as a cushion between everything on the inside. Visceral fat is much harder to measure, and also much harder to loose. Your body sees your subcutaneous fat as an energy warehouse, but views you visceral fat more like bubble wrap for your important parts. That is why it seems like you have lost all the fat from your arms and legs (subcutaneous) but still have fat around your mid section (visceral). Just keep working hard and watching what you eat, your body will let your subcutaneous fat get very low before it starts tapping into your visceral fat stores.