The fat inside the abdomen will take up relatively more space after the tightening of the abdominal wall, and you will feel full faster when you eat. This may function as an external "lap-band"
This may help with further weight loss after the surgery. Many of my patients have mentioned this.
This may contribute to the post-op result after several months, especially if you are motivated to lose weight.
If the fat excess is extreme I would also recommend losing weight before however.