How they can slow weight loss, even on an apparently ‘healthy’ diet
A new clinical trial from the UK suggests that ultra-processed foods (UPFs) make it harder to lose weight, even when the total calories and nutrient content consumed meet healthy-eating guidelines.[1]
In the 8-week study, 55 adults followed two versions of the UK’s Eatwell diet: one based on minimally processed foods (MPFs) and the other on ultra-processed foods. Both diets led to weight loss — but participants lost nearly twice as much weight on the minimally processed version (about 2% of body weight) compared to the ultra-processed one (about 1%).
What are minimally processed foods (MPFs)
These are foods that are close to their natural form, undergoing little more than cleaning, cutting, freezing, or simple cooking. Everyday examples include fresh or frozen fruit and vegetables, plain yogurt, fresh meat and fish, eggs, whole grains and nuts or seeds without added sugar or chemical flavourings.
By contrast, ultra-processed foods (UPFs) are made from refined ingredients – think white flour where the bran and germ have been removed to increase shelf life and reduce spoiling. Then combine this with assorted man-made additives, such as colourings, flavourings, emulsifiers and thickeners, and you have ultra-processed foods. Our supermarkets are overflowing with UFPs – packaged snack foods, breakfast cereals, instant noodles, sweetened yogurts, chicken nuggets or tater tots, and ready meals.
It’s not just about counting calories
The findings of this study underscore that when it comes to weight loss, calories aren’t the whole story. Diets high in UPFs — which over the last few decades have come to dominate food intake in the UK, North America, and much of Europe — are linked not only to slower weight loss and obesity, but also heart disease, cancer and an increased likelihood of developing dementia. [2]
So, swapping ultra-processed items for real, minimally processed foods could be more than just a helpful hand in maximizing weight loss, it may be one of the simplest and most rewarding steps you can take to ensure lasting all-round health benefits.
[1]. Dicken SJ, et al. Nature Medicine. 2025; https://doi.org/10.1038/s41591-025-03842-0
[2]. Wang DD, et al. Global Improvement in Dietary Quality Could Lead to Substantial Reduction in Premature Death. J Nutr. 2019 Jun 1;149(6):1065-1074
