There are a lot of possible explanations for why Japan has weathered the COVID-19 pandemic better than the United States. It’s possible that the Japanese are more used to wearing masks, that the government used contact tracing more effectively to contain outbreaks, and that handshakes aren’t a widespread cultural practice. But according to Dariush Mozaffarian, a cardiologist, and the dean of the Tufts Friedman School of Nutrition Science and Policy, one of the main reasons Japan is coping with the coronavirus more successfully than the United States is because of another problem: obesity.

America has one of the highest rates of obesity in the developed world, and Japan has one of the lowest. And it’s this major health concern that’s making America’s response to COVID-19, much more difficult. Mozaffarian explains why that is, and the ways we can deal with it.