A paradigm-shifting diet book that explains why one-size-fits-all diets don't work and helps readers customize their diet to lose weight and improve health. There are certain things we take as universal truths when it comes to dieting and health: kale is good; ice cream is bad. Until now. When Drs. Segal and Elinav published their groundbreaking research on personalized nutrition, it created a media frenzy.