When thin people see someone who is overweight, many of them assume it's because all overweight people are slothful gluttons.

Anyone intelligent person knows this is not true. Some people are born lucky, with a metabolism that lets them eat almost anything without putting on weight. Other people are born with a metabolism that would be great in a world where calories were scarce: they are very efficient at converting calories to fat, which can store the calories until food is scarce. Then...