We’ve heard it a million times: “Eat a well-balanced diet with everything in moderation.” After all these decades of clear failure, it’s a hazy cliché still delivered by physicians, dietitians and nutritional “experts” with earnest assurance. The same goes for exercise and stress. Moderate amounts of stress are okay, moderate cardiovascular work is good, etc. We accept the concept of moderation so readily, I think, because it sounds so rational and simple. If we follow common sense, moderation suggests, we’ll be fine. But if it were that easy, most people would be healthy—and statistics on the rising rates of obesity and chronic illness tell us otherwise. So what’s the problem?