We All Know Processed Food is Bad for You, But Now There’s Proof

It’s no secret that, despite how good it may taste, processed food isn’t the healthiest option when it’s time to consider what to pack onto your plate. But surprisingly, until now, there hadn’t been much data to support this claim. Researchers and nutritionists have long theorized that ultra-processed food, in addition to being high in calories, sugar and fat while also low in fiber, cause you to overeat.

To test this theory, researchers at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recruited 20 volunteers, evenly split by gender, to be observed for 28 straight days in a special wing of the NIH Clinical Center. Instead of just observing what people ate, the researchers prescribed and controlled every meal, as well as the amount of daily exercise the participants received. For the first two weeks, half of the participants ate strictly unprocessed foods, while the other half ate ultra-processed foods. Every meal contained twice the calories participants would need to maintain their body weight, and they were all told to eat as much or as little as they wanted. The groups then swapped meal plans for the final two weeks of the study. It’s important to note that each meal was matched in terms of macros, meaning that, regardless of which diet the participants were on, each meal contained approximately the same number of carbs, fat, protein, fiber, sugar, and total calories.

The researchers found that participants eating the ultra-processed foods consumed an average of 508 calories more per day, mostly in the form of carbs and fat, with protein intake and total fiber and sugar consumptions remaining the same. The extra calories added almost a pound of weight to the participants’ baseline weights. On the flip side, those eating unprocessed food lost an average of the same amount during the same timeframe.

The researchers theorize part of this different may have been due to changes in appetite and the speed at which participants ate, depending on the diet they were on. While this study doesn’t necessarily answer why some people overindulge in ultra-processed foods, this study suggests that what whole foods people can work in to their diets, they should.

Read the in Cell Metabolism.