Doctor and journalist Chris van Tulleken wanted to know how ultra-processed foods affect us, so for a month he ate almost nothing but UPFs. His book Ultra-Processed People examines how the food we eat today is dramatically changing our bodies and minds. This episode was produced by Siona Peterous, edited by Matt Collette, fact-checked by Isabel Angell, engineered by Patrick Boyd, and hosted by Noel King. Transcript at vox.com/todayexplained Support Today, Explained by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices