The evidence that ultra-processed foods are bad for us is piling up. But efforts to reduce their role in our diets face a big hurdle: experts can't agree on what they are and which to target.

Americans get about 55% of our calories from tasty, cheap — and unhealthy — manufactured foods, the latest data from CDC says. For kids, the percentage is even higher.

Kids in the U.S. get most of their calories from ultra-processed foods, which are tied to health problems. Now, scientists are finding that kids don't all react to these foods in the same way.

Americans consume more than half their daily calories from ultra-processed food. A new study finds consuming lots of this food is linked to a higher risk of many diseases.

A diet composed of 80% ultra-processed foods led one British doctor to gain weight and feel unwell. Now he's trying to nail down the health effects of this type of diet, which many Americans eat.

Sure, they're tasty, but packaged snacks and meals can be packed with sugar, salt and a list of unpronounceable ingredients. So what are they doing to your health? Scientists are trying to find out.