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 the airport's website to gain additional insight. Most airlines suggest arriving two to three hours early for a flight to Canada. If the airport is small, closer to two hours early is often sufficient. For many airlines, the minimum check-in time is 30 to 45 minutes before the flight leaves, but all airlines recommend you arrive well before this time.