For a lucky few people in the world, weight will never be a source of worry.
People who have a rare genetic mutation called essential fructosuria lack the primary enzyme needed to metabolize fructose, a natural sugar found in honey, fruits and vegetables. No ill consequences have been linked to the defect, save for an aversion to sweets, and it appears to have a significant benefit: Those who have it seem to be at little risk of obesity, type 2 diabetes or serious liver ailments.