“You can ignore reality, but you can’t ignore the consequences of ignoring reality.”
―Ayn Rand
Recently, in both the UK and the US, the latest dietary guidelines opted not to include recommendations specifically geared towards addressing the consumption of ultraprocessed foods (UPFs). In the UK, the Scientific Advisory Committee on Nutrition (SACN) and the 2025 US Dietary Guidelines for Americans Committee (DGAC) both reported that there was insufficient evidence to include addressing ultra-processed foods within dietary guidelines. It is well-established that higher levels of ultraprocessed food consumption correlate with increased risks of chronic disabilities and diseases such as obesity, type II diabetes, cardiovascular disease, mental health and cognitive issues, as well as an increased risk of early mortality. Given that well over 50% of the food consumed in the UK, and upwards of 60-70% of the food consumed in the United States, falls into the ultraprocessed food category, this would seem to warrant serious consideration. Both advisory groups highlighted a need for further interventional randomized controlled trials to demonstrate evidence before such potential recommendations can be considered. This week’s Study Spotlight highlights a trial designed to do just that.
- The study reported findings from the “Ultra processed versus minimally processed diets following UK dietary guidance on health outcomes” (UPDATE) trial, a landmark randomized controlled trial published in Nature Medicine.
- The study examined two approaches to following the UK’s Eatwell Guide (EWG), which focuses on macronutrients (for example, fat, protein, and carbohydrates) and food groups (for example, fruits and vegetables, dairy, and starchy foods), but not UPFs.
- One diet was minimally processed foods (MPF), and the other was a diet rich in ultraprocessed foods (UPF).
- The trial demonstrated that while both a minimally processed food (MPF) diet and an ultra-processed food (UPF) diet designed to meet the UK’s healthy Eatwell Guide recommendations resulted in weight loss over eight weeks, the MPF diet produced significantly greater weight loss, primarily driven by a reduction in body fat.
The Caveat:
The global rise in obesity and related non-communicable diseases has been linked to significant changes in the food environment, particularly the increased consumption of ultraprocessed foods (UPFs, as classified by the NOVA Classification Group 4). UPFs are industrial formulations, such as breakfast cereals, sweets, and mass-produced bread, which account for over 50% of the energy intake in the UK and a significantly higher percentage in the United States.
The UPDATE trial was designed to help fill the critical evidence gap between correlation and causality. Its primary objective was to compare the effects of an 8-week MPF diet versus an 8-week UPF diet on percentage weight change, with both diets being designed to meet the UK’s official Eatwell Guide (EWG) recommendations.
The UPDATE trial was a single-center, community-based, 2 × 2 crossover, randomized controlled trial. The group consisted of 55 adults (50 in the final intention-to-treat analysis) in the UK with a Body Mass Index (BMI) of ≥25 to <40 kg m−2 and a habitual UPF intake of ≥50% of daily calories. The participants were provided with all meals, snacks, and drinks for two distinct 8-week diet periods in a random order, being placed on both a Minimally Processed Food (MPF) Diet and an Ultra-Processed Food (UPF) Diet. Both diets were matched for and adhered to the UK Eatwell Guide’s recommendations for macronutrients, fiber, sugar, salt, and fruit/vegetable intake. Diets were provided ad libitum, meaning participants could eat as much or as little as they desired. A 4-week washout period, during which participants returned to their habitual diet, separated the two intervention periods to minimize carryover effects. Importantly, the participants were not informed about the processing level of the diets (referred to as Diet A and Diet B) and were blinded to the primary outcome of weight change (i.e., participants were blinded to the type of diet when reporting).
The central finding of the trial was a statistically significant difference in weight loss between the two diets. It is essential to recognize that both diets led to weight loss from baseline, suggesting that adopting a diet in line with the Eatwell Guide is effective for weight management, regardless of whether the food groups consumed are ultraprocessed or not. However, the MPF diet resulted in almost twice the weight change of the UPF diet (-2.06% versus -1.05%), a statistically significant value.
Interestingly, the study revealed that the nature of the weight lost differed significantly between the diets. The MPF diet led to significant reductions in fat mass (−0.98 kg), body fat percentage (−0.76%), and visceral fat rating (−0.41). These reductions were significantly greater than those on the UPF diet. The UPF diet did not produce a statistically significant decrease in any measure of adiposity (fat mass, body fat percentage, or visceral fat). The superior weight loss on the MPF diet was primarily due to the loss of body fat, a critical factor in improving obesity-related health risks. Changes in fat-free mass did not differ between the diets.
The study also examined the effects of diet on behavioral variables. The MPF diet resulted in significantly greater improvements in craving control, reduced craving for savory foods, and enhanced ability to resist cravings. Not surprisingly, the self-reported energy intake was significantly lower on the MPF diet compared to the UPF diet (a difference of -327.3 kcal/day). This aligns with the observed greater weight loss. Unlike findings in prior studies, in the UPDATE trial, participants rated the “flavors and tastes” and “delivery and preparation” of the MPF diet significantly lower than those of the UPF diet. Despite finding the MPF diet less palatable, they still consumed fewer calories and lost more weight. Such findings are understandable when viewed through the lens of UPF construction as hyperpalatable comestibles. Despite being tastier, UPFs induced a higher incidence of gastrointestinal complaints (including constipation and dyspepsia/reflux), fatigue, and sleep-related issues.
The findings of the UPDATE trial have profound implications for public health, nutrition science, and dietary policy. This trial adds to the growing body of evidence that, quite simply, processing matters. The study provides evidence to support the hypothesis that the level of food processing is an independent factor influencing health outcomes, even when diets are nutritionally equivalent according to official guidelines. Removing UPF provided benefits for weight and fat loss beyond those achieved by simply following nutrient-based recommendations.
The UPF diet, despite meeting the criteria of the EWG to be deemed nutritionally “healthy,” is likely driven by characteristics inherent to UPFs that result in less healthful outcomes. These results strongly support the argument for addressing UPFs within the context of national dietary guidelines. A sole focus on nutrients, the current modus operandi, appears insufficient to address the drivers of chronic disability and disease fully. The discussion needs to expand to include the role of the broader food system and industrial food production in shaping an environment that leads to the poor health of entire populations.
The Study:
Additional references:
Dietary Guidelines for Americans. 2025 Dietary Guidelines Advisory Committee: Meeting 5 (USDA, 2024).
Monteiro, C. A. et al. Ultra-processed foods: what they are and how to identify them. Public Health Nutr. 22, 936–941 (2019).
Phelps, N. H. et al. Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults. Lancet 403, 1027–1050 (2024).
Popkin, B. M. & Ng, S. W. The nutrition transition to a stage of high obesity and noncommunicable disease prevalence dominated by ultra-processed foods is not inevitable. Obes. Rev. 23, e13366 (2022).
Popkin, B. M., Adair, L. S. & Ng, S. W. The global nutrition transition: the pandemic of obesity in developing countries. Nutr. Rev. 70, 3–21 (2012).
Rauber, F. et al. Ultra-processed food consumption and indicators of obesity in the United Kingdom population (2008–2016). PLoS ONE 15, e0232676 (2020).
The Global BMI Mortality Collaboration. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. Lancet 388, 776–786 (2016).
