Minimally Processed Diet Linked to Greater Weight Loss Than Ultra-Processed Diet in Randomized Trial

While traditional nutrition focuses on macronutrients, recent evidence suggests that higher consumption of UPF correlates with increased noncommunicable disease risks; however, a significant clinical gap remains regarding the health impact of processing levels within the context of established dietary guidelines. To address this, Samuel J. Dicken from University College London (UCL) aimed to compare the health effects, primarily %WC, between 8-week MPF and UPF diets that both strictly adhered to the UK Eatwell Guide (EWG) recommendations.

To address this gap, Samuel J. Dicken from University College London (UCL) and colleagues conducted a 2×2 crossover randomized controlled feeding trial titled “Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health.” The study enrolled 55 adults in England with a body mass index (BMI) ≥25 to <40 kg/m² and habitual UPF intake of at least 50% of daily energy intake. Twenty-eight participants were randomized to receive the MPF diet first, followed by the UPF diet, and 27 followed the reverse order. Fifty participants comprised the intention-to-treat analysis sample.

Participants were provided with two 8-week ad libitum diets in random order. Both dietary patterns were designed to align with the UK Eatwell Guide recommendations. The primary endpoint was the within-participant difference in percent weight change (%WC) from baseline to week 8. Participants were blinded to the primary outcome.

Key Clinical Findings of the Study Include:

• Weight Reduction Superiority: The UPDATE study demonstrated that MPF led to a significantly greater decrease in weight and BMI, with a difference of -0.96 kg (P=0.019) and -0.34 kg m⁻² (P=0.021), respectively, compared to UPF.
• Pronounced Adiposity Loss: Reductions in fat mass were significantly more pronounced on the MPF diet, showing a -0.98 kg difference over the UPF intervention.
• Lipid Profile Divergence: While MPF resulted in a significantly greater reduction in triglycerides with a -0.25 mmol l⁻¹ difference,, the UPF diet showed lower low-density lipoprotein cholesterol (LDL-C) by 0.25 mmol l⁻¹.
• Heightened Craving Control: Participants on the MPF diet experienced significantly greater improvements in Control of Eating Questionnaire (CoEQ) craving control scores, with an 11.68-point advantage over those on the UPF diet.

The results suggest that while both guideline-compliant diets produced weight loss, the MPF diet was more effective, achieving a mean within-participant difference in %WC of -1.01% (P=0.024) over eight weeks.

The study concludes that clinical dietary recommendations could benefit from incorporating guidance on food processing levels alongside existing macronutrient and food group targets to improve weight management outcomes.

Although the free-living design offers real-world applicability, the potential for carryover effects and the exclusion of individuals with specific dietary restrictions remain limitations, highlighting the value of future research to confirm these exploratory secondary findings.

Reference

Dicken, S. J., et al. (2025). Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial. Nature Medicine. https://doi.org/10.1038/s41591-025-03842-0.