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.
Check with your airline and the airport you are flying out of for their recommendations on how early to arrive for an international flight. In general, plan to arrive somewhere between two and three hours before your scheduled flight departure time.