The suspect that was ignored

In 1972 a British physiologist named John Yudkin published a book with a title that told you where he stood: Pure, White and Deadly. His claim, built on decades of research, was that sugar, not fat, was the dietary cause of the heart disease, obesity and diabetes rising across the West. He was ridiculed, his career was damaged, and the field went on to spend forty years blaming fat.

He was mostly right. In 2012 a pediatric endocrinologist named Robert Lustig picked the argument back up in Fat Chance, and by 2015 the World Health Organization had put a number on it: free sugars, meaning added sugars and the sugar in juice and honey, should be under ten percent of daily calories, with five percent as the better target. For most adults that's about twenty-five to fifty grams a day. A single can of soda is about forty.

The science that vindicated Yudkin is now broad. Added sugar, especially in drinks, drives weight gain, insulin resistance, fatty liver and the whole cluster of metabolic disease, and it does it partly by bypassing the fullness signals that solid food triggers. Fat, meanwhile, turned out to be a far more complicated story than the low-fat decades allowed.

It's a table key because sugar is the single ingredient whose removal does the most for the most people, and because it hides. Bread, sauces, yogurt, cereal, anything labeled low-fat: the sugar is in there, by the gram, and most people have no idea how much they eat. The honest number, counted for a day, is usually a shock.

And it's a story about how long a right answer can be ignored. Yudkin died in 1995, before the field came round.