It all started in the summer of 2023, when author and infectious-disease physician Dr. Chris van Tulleken was promoting his book, Ultra-Processed People. While writing it, van Tulleken spent a month eating mostly foods like chips, soda, bagged bread, frozen food, and cereal. “What happened to me is exactly what the research says would happen to everyone,” van Tulleken says: he felt worse, he gained weight, his hormone levels went crazy, and before-and-after MRI scans showed signs of