University of Liverpool Study Tracks Long-Term Effects of Diet Soft Drinks

Metabolic Changes Emerge After Two Years of Daily Consumption

Researchers at the University of Liverpool have completed the longest randomized controlled trial to date examining the long-term health impacts of non-nutritive sweetened beverages. The 104-week clinical study, concluded in September 2026, followed participants consuming either sugar-sweetened or artificially sweetened soft drinks to assess metabolic and health outcomes over two years.

Non-nutritive sweeteners, including aspartame, sucralose, and stevia, are widely used as low- or no-calorie sugar substitutes in foods and beverages. While marketed as healthier alternatives for weight management and diabetes prevention, their long-term safety and physiological effects remain debated among health professionals and consumers alike.

The trial tracked over 200 adults aged 18 to 65, randomly assigned to consume either sugar-sweetened or non-nutritive sweetened beverages daily for 104 weeks. Researchers monitored body weight, waist circumference, blood pressure, cholesterol levels, and markers of glucose metabolism throughout the study period.

Lead researcher Dr. Sarah Mitchell noted that participants drinking NNS beverages showed modest increases in appetite and cravings compared to those consuming regular sodas. However, no significant differences in weight gain or metabolic syndrome incidence were observed between the two groups at the study's conclusion.

Blood tests revealed slight elevations in certain inflammatory markers among the NNS group, though researchers emphasized these changes remained within normal clinical ranges. Liver enzyme levels stayed stable across both cohorts, suggesting no immediate harm from prolonged artificial sweetener consumption.

Do Artificial Sweeteners Disrupt Natural Appetite Regulation?

The findings add to growing scientific uncertainty about whether non-nutritive sweeteners truly support weight loss goals over extended periods. Previous studies have produced conflicting results, with some linking artificial sweeteners to increased cardiovascular risk while others show neutral or beneficial effects.

Dr. Mitchell explained that the disconnect between expected and observed outcomes may stem from individual variations in gut microbiome composition, which can influence how different sweeteners affect digestion and metabolism.

Participants reported similar satisfaction levels with both beverage types, though those consuming NNS drinks expressed concerns about artificial ingredients despite understanding the study's purpose.

Looking ahead, the research team plans to investigate genetic factors that might predict better responses to artificial sweeteners. They also aim to examine whether combining NNS beverages with other dietary interventions produces different long-term outcomes.

Health officials continue recommending water as the primary beverage choice, while acknowledging that non-nutritive sweetened drinks may serve as a transitional tool for people reducing sugar intake.

Are diet sodas safe to drink long-term?

Frequently Asked Questions

Current evidence suggests moderate consumption poses minimal risk for most healthy adults, though individual responses vary significantly based on genetics and overall diet quality.

Do artificial sweeteners cause weight gain?

This study found no significant weight differences between groups over two years, though some participants reported increased appetite after consuming NNS beverages.

Which sweeteners are considered safest?

Stevia and monk fruit are plant-based options with extensive safety testing, while aspartame and sucralose remain approved by major health authorities within acceptable daily intake limits.