Ultra-Processed Foods and Obesity: What the Latest Research Shows

Ultra-processed foods (UPFs) are industrial formulations made from extracted food substances — refined starches, sugars, fats, and protein isolates — combined with additives including emulsifiers, flavour enhancers, colourings, and preservatives. They include packaged snacks, ready meals, breakfast cereals, soft drinks, reconstituted meat products, and many breads and pastries. According to data from the National Diet and Nutrition Survey, UPFs account for approximately 57% of total calorie intake in UK adults — one of the highest proportions in Europe.

How are UPFs defined?

The most widely used classification system is the NOVA framework, developed by researchers at the University of São Paulo. NOVA divides foods into four groups based on the extent and purpose of processing, with Group 4 (ultra-processed) defined by the presence of industrial additives not used in home cooking. The NOVA system has been adopted by the Pan American Health Organization and is increasingly used in UK and European nutritional research.

What does the research show about UPFs and obesity?

Evidence linking UPF consumption to weight gain and obesity has grown substantially in recent years. A landmark randomised controlled trial published in Cell Metabolism in 2019 by Hall and colleagues at the US National Institutes of Health directly compared ad libitum consumption of ultra-processed versus unprocessed diets in a controlled inpatient setting. Participants on the ultra-processed diet consumed an average of 508 kcal per day more and gained 0.9kg over two weeks, while those on the unprocessed diet lost 0.9kg.

Large prospective cohort studies have reinforced these findings. A 2019 study in PLOS Medicine following over 100,000 French adults found that a 10% increase in the proportion of UPFs in the diet was associated with a 12% increase in the risk of overweight and obesity. A 2024 umbrella review of 45 meta-analyses published in the British Medical Journal found consistent associations between UPF consumption and 32 adverse health outcomes, including obesity, type 2 diabetes, cardiovascular disease, and all-cause mortality.

Why do UPFs promote overconsumption?

Several mechanisms have been proposed. UPFs are typically energy-dense, low in fibre, and engineered to be highly palatable — combinations of fat, sugar, and salt that activate reward pathways in the brain. They are also rapidly digested, producing sharp glucose spikes followed by hunger-promoting dips. Emulsifiers may disrupt the gut microbiome and impair satiety signalling. The soft texture of many UPFs reduces chewing time, which is associated with faster eating and reduced satiety.

What are the practical implications?

Reducing UPF consumption does not require a perfect diet. Practical steps include cooking from whole ingredients where possible, choosing minimally processed alternatives (e.g. plain oats over sweetened cereals, whole fruit over fruit juice), reading ingredient lists, and being aware of UPF-heavy meal patterns such as frequent takeaways and packaged snacks.

For personalised dietary guidance as part of a doctor-led weight management programme, book a consultation with Weight Loss Wales.