But the gene doesn’t seem to have always been a problem. If scientists had studied FTO just a few decades ago, they would have found no link to weight whatsoever. A new study shows that FTO became a risk only in people born after World War II. The research, published this week in the Proceedings of the National Academy of Sciences, raises questions that extend far beyond obesity. Genes clearly influence our health in many ways, but so does our environment; often, it is the interplay between them that makes the difference in whether we develop obesity or cancer or...