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Introduction
Recently a new trial was published in Nature Medicine comparing the effect of ultra-processed versus minimally processed diets. Specifically, the UPDATE trial compared these two diets in the context of a healthy dietary pattern (in line with the UK’s EatWell Guide).
This eight-week randomized, crossover trial generated a lot of discussion and was largely seen as being a really useful addition to the evidence base, and providing answers to some previously unexamined questions.
In this episode the study’s lead author, Dr. Samuel Dicken, explains the background context for the UPDATE trial, provides an insight into its execution, and puts some of the results in context. There is also a discussion about the current state of evidence more broadly and the leading hypotheses around the mechanisms that drive the observations seen with consuming ultra-processed foods.
This episode is particularly noteworthy because it provides fresh evidence on an important question: does following dietary guidelines with minimally processed foods confer extra benefits over following the same guidelines with ultra-processed foods?
Related resources
- Join the Sigma newsletter for free
- Subscribe to Sigma Nutrition Premium
- Enroll in the next cohort of our Applied Nutrition Literacy course
- Study: Dicken et al., 2025 – Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial
- LinkedIn: Samuel Dicken
- X: @SamuelDickenUK
- [02:48]Interview with Dr. Samuel Dicken
- [03:08]Background and research interests of Dr. Samuel Dicken
- [04:31]Details of the update trial
- [09:48]Trial design and methodology
- [15:45]Results and findings of the update trial
- [18:46]Secondary outcomes and craving control
- [25:43]Hypotheses and mechanisms behind UPF effects
- [40:28]Policy implications and future research directions
Guest Information
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Samuel Dicken is a Research Fellow in the Department of Behavioural Science and Health and the Centre for Obesity Research at University College London, where his work focuses on how diet, exercise, and lifestyle shape metabolism, body composition, and long-term health, particularly in relation to cardiovascular disease.
Dr. Dicken trained as a Registered Clinical Scientist through the NHS, specialising in vascular science, before later pursuing his PhD as part of the Medical Research Council’s Doctoral Training Programme at UCL.
Danny Lennon has a master’s degree (MSc.) in Nutritional Sciences from University College Cork, and he is the founder of Sigma Nutrition.
Danny is currently a member of the Advisory Board of the Sports Nutrition Association, the global regulatory body responsible for the standardisation of best practice in the sports nutrition profession.
Introduction to this Episode
Recently a new trial was published in Nature Medicine comparing the effect of ultra-processed versus minimally processed diets. Specifically, the UPDATE trial compared these two diets in the context of a healthy dietary pattern (in line with the UKʼs EatWell Guide).
This eight-week randomized, crossover trial generated a lot of discussion and was largely seen as being a really useful addition to the evidence base, and providing answers to some previously unexamined questions.
In this episode the studyʼs lead author, Dr. Samuel Dicken, explains the background context for the UPDATE trial, provides an insight into its execution, and puts some of the results in context. There is also a discussion about the current state of evidence more broadly and the leading hypotheses around the mechanisms that drive the observations seen with consuming ultra-processed foods.
This episode is particularly noteworthy because it provides fresh evidence on an important question: does following dietary guidelines with minimally processed foods confer extra benefits over following the same guidelines with ultra-processed foods?
Useful Terminology for this Episode
- Ultra-Processed Food (UPF): In the NOVA classification system, UPFs are those at level 4 and are made using industrial formulations made mostly from ingredients not used in home cooking (e.g. refined extracts, additives).
- Minimally Processed Food (MPF): Foods in their natural or near-natural state, undergoing minimal alteration. These include whole or simple processed items like fresh fruits and vegetables, whole grains, meat, milk, or foods prepared from basic ingredients (e.g. homemade soup).
- NOVA Classification: A food classification system that groups foods by their level of processing, from Group 1 (unprocessed or minimally processed) to Group 4 (ultra-processed). NOVA Group 4 foods (UPFs) include items like sugary drinks, packaged snacks, instant noodles, and reconstituted meat products. This system, developed by Carlos Monteiro and colleagues, is used in research to study diet processing levels. NOVA goes beyond nutrient content, considering the purpose and extent of processing.
- Randomized Crossover Trial: A study where participants are randomly assigned to receive interventions in a sequence. In this case, each person consumed both the MPF and UPF diet in random order, acting as their own control. A crossover design improves statistical power and reduces between-person confounders. (A washout period is included between diets to minimize carryover effects.)
- Ad libitum Diet: An eating regimen where individuals eat as much or as little as desired, rather than a fixed calorie allotment. In this trial, both diet phases were ad libitum – participants had abundant food provided and were instructed to eat to their appetite with no calorie restriction.
- Energy Density: The amount of calories per gram of food. Ultra-processed foods are often energy-dense (high in calories for a small volume) due to added sugars and fats. Foods with high energy density can promote excess calorie intake before fullness signals kick in. By contrast, whole foods (fruits, vegetables, etc.) tend to be less energy-dense and more filling per calorie.