At 285 pounds and 5 feet 7 inches, I may not be the tallest, but I am almost always one of the biggest passengers on a plane. That’s “one of”: as anyone with even the most tangential relationship with news headlines over the last several years knows, Americans are getting fatter and fatter. .. “How many kilos you weigh?” asked a customs officer at Ho Chi Minh Airport when I visited Vietnam a few years ago. “Is that a question on the form?” I responded, slightly unnerved. Smiling, she told me no. She was apparently just curious. After giving me...