Here's the deal: Yes, your metabolism affects your size, and the faster your personal motor runs, the more calories you'll burn. But the truth is, a slow metabolism isn't the real reason you're packing on pounds. You are the reason.
As a general rule, arrive at the airport no later than two hours before your domestic flight is scheduled to depart. This is somewhat later than the typical suggestion of three hours for an international flight.
Arriving 2 to 3 hours early is unnecessary and neurotic. 1.25 hours is optimal. That is plenty of time to check in, go through security, find the gate and sit down and wait to board. Eat something before you go to the airport and make sure to use the airport's facilities at least 15 minutes before boarding the plane.