A common explanation is that people who are overweight have more energy reserves to fight off illness. They are like contestants on the television show Survivor, says Gregg Fonarow, a cardiologist at the University of California, Los Angeles: "Those that started off pretty thin often don't come out successful."Metabolic reserves could also be important as people age. "Survival is a balance of risks," says Stefan Anker, a cardiology researcher at Charit Medical University in Berlin.WEEK 17 SHOULD MEAN SOMETHING: The NFL can't guarantee every seasonending game will be competitive as teams with their playoff standings secured rest starters, a la the 2009 Indianapolis Colts. But scheduling division matchups for Week 17 could force some squads to take the games more seriously because the results may carry extra weight in terms of playoff seeding and homefield advantage. The most intriguing matchups on paper are Dallas at Philadelphia, Arizona at San Francisco, Miami