In a small randomized controlled trial, people lost twice as much weight when their diet was limited to minimally processed food compared to when they switched to a diet that included ultraprocessed versions of foods but was otherwise nutritionally matched.
The trial, published in Nature Medicine by researchers at University College London, adds to a growing body of evidence that food processing, in addition to simple nutrition content, influences our weight and health. Ultraprocessed foods have already been vilified for their link to obesity—largely through weaker observational studies—but researchers have struggled to shore up the connection with high-quality studies and understand their impact on health.
The ultraprocessed foods researchers provided in the new trial were relatively healthy ones—as ultraprocessed foods go. They included things like multigrain breakfast cereal, packaged granola bars, flavored yogurt cups, fruit snacks, commercially premade chicken sandwiches, instant noodles, and ready-made lasagna. But, in the minimally processed trial diet, participants received meals from a caterer rather than ones from a grocery store aisle. The diet included overnight oats with fresh fruit, plain yogurt with toasted oats and fruit, handmade fruit and nut bars, freshly made chicken salad, and from-scratch stir fry and spaghetti bolognese.
