A new study published in Nature Medicine reveals that not all calories behave the same when it comes to weight loss. Researchers from London’s Centre for Obesity Research found that people who followed a diet based on minimally processed foods lost up to twice as much weight as those eating ultra-processed products, even when total calories were the same.
The findings highlight what many nutrition experts have long suspected: food quality matters just as much as quantity. According to the researchers, ultra-processed foods not only provide empty calories but also interfere with how the body regulates hunger, satiety, and metabolism.
The trial involved adults with overweight and obesity who were assigned to two diets containing identical amounts of calories, fat, carbohydrates, and protein. The only difference was the level of food processing. After several weeks, participants eating minimally processed foods showed significantly greater weight loss, along with improvements in metabolic measures such as blood sugar control.
Scientists suggest that ultra-processed products — packed with additives, added sugars, and industrial fats — tend to overstimulate appetite and push people to eat more than they need, even when they are not truly hungry. In contrast, fresh, minimally processed foods such as vegetables, meat, eggs, whole grains, and simple dairy products promote natural satiety and help the body maintain a healthier energy balance.
This study also connects to a larger discussion happening worldwide about the role of ultra-processed foods in obesity and chronic disease. Nearly three billion people globally live with overweight or obesity, conditions strongly tied to non-communicable diseases and premature death. Researchers point to changes in the food environment as a major cause, especially the rise of ultra-processed products. In places like the UK, USA, and Europe, over half of daily calories now come from these foods.
Health organizations such as the World Health Organization and countries like Brazil recommend reducing UPF consumption. Yet, in the UK, almost two-thirds of adults live with overweight or obesity, and fewer than 1 in 1,000 follow the official dietary recommendations in full. Until recently, guidelines such as the UK’s Eatwell Guide or the U.S. Dietary Guidelines had not included UPFs explicitly, arguing that stronger evidence was needed.
That’s why the new UPDATE trial (“Ultra processed versus minimally processed diets following UK dietary guidance on health outcomes”) was designed: to provide the high-quality evidence health authorities were waiting for. The trial compared 8-week diets based on ultra-processed foods and minimally processed foods, both designed according to the UK’s dietary guidelines. The primary goal was to measure weight changes, but researchers also looked at body fat, metabolic markers, and appetite.
The results send a clear message: fighting obesity and improving health requires more than just counting calories. What truly matters is the kind of food on the plate and how much it has been processed.
Source: Nature Medicine
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