In this exclusive preview of Gary Taubes’ new book, Taubes explains why most of us have a fraught relationship with food and a flawed understanding of what makes a healthy diet. Here Taubes argues, “The existing evidence says that if you have metabolic syndrome, if you’re getting fatter or are already obese, if you’re prediabetic or already diabetic, avoiding carbohydrate-rich foods and replacing them with fat may be the single healthiest thing you can do for yourself." He adds: "No one can guarantee what happens in the long run. … Anyone who makes an ironclad guarantee for any way of eating—that one diet will assuredly make you live longer than others ... is probably selling something."