Study Reveals Weight Loss Benefits of Minimally Processed Foods

A recent small randomized controlled trial found that individuals lost double the weight on a diet of minimally processed foods compared to a nutritionally equivalent diet featuring ultraprocessed foods. This research, published in Nature Medicine by scientists at University College London, contributes to a growing understanding of how food processing impacts weight and overall health, alongside nutrition. Ultraprocessed foods have already drawn criticism for their association with obesity, although previous studies were often observational and less rigorous in design. Researchers are now looking to solidify the connection through higher-quality studies.

In this study, the ultraprocessed foods provided were relatively healthier choices, featuring items like multigrain cereals, granola bars, flavored yogurt, fruit snacks, commercially prepared chicken sandwiches, instant noodles, and pre-made lasagna. In contrast, the minimally processed food group received meals prepared by a caterer, which included overnight oats with fresh fruit, plain yogurt topped with oats and fruit, handmade fruit and nut bars, freshly made chicken salad, and scratch-made stir fry as well as spaghetti bolognese.

Although the processing levels between the two diets were distinct, both diets had comparable nutritional balances in terms of fat, protein, carbohydrates, and fiber, along with similar proportions of fruits, vegetables, dairy, and starchy foods. Overall, each diet aligned with the UK government’s dietary guidelines known as the Eatwell Guide (EWG).

Study Design

The trial utilized a crossover design, which meant participants were randomly assigned to begin on either the ultraprocessed or minimally processed diet. They followed their initial diet for eight weeks before taking a break and then switching to the other diet. Food was delivered to their homes, allowing participants to eat according to their preferences, and they largely adhered to their designated diets, as indicated by food diaries.

Out of the original group, fifty participants completed at least one diet, while 43 finished both. The majority were women, averaging 43 years in age, and all had body mass indexes that fell within the overweight or obese categories. At the trial’s outset, ultraprocessed foods constituted nearly 70 percent of their regular diets, and these participants were not compliant with EWG guidelines.