Diet drinks, in particular, diet soda, have been in the crosshairs of the weight loss industry for decades. All sort of negative implications have maligned them publicly and doubt about them is nearly universal. Water was given the “OK” to be the beverage of choice for a weight-loss conscious group of adults. Researchers from the University of Liverpool set out to determine whether water or diet drinks had more effect on weight loss, and if chronic use had any effect on other markers.
A group of 493 patients with BMI’s between 27-35 were followed for 104 weeks (2 years). Half of them drank two 330-mL servings of water daily, and the other half drank the same amount of diet drinks sweetened with aspartame, acesulfame, and sucralose. All study participants were placed on a “behavioral weight management program.”
At week 104, the amount of weight both groups lost was very similar: 3.7 kg (8.14 lbs) for water and 4.8 kg (10.56 lbs) for diet drinks. The difference was not considered statistically significant.
Waist circumference decreased in both groups: 4.5 cm (1 and 3/4th inches) for water and 5.5 cm (2 and 1/8th inches) for diet drinks. These were not statistically significant, either.
Biomarkers cholesterol, A1C, and diastolic BP were affected as well:
Cholesterol rose by 0.2 mmol/L for diet drinks and fell by 0.3 mmol/L for water.
A1C rose by 1.8 mmol/mol for diet drinks and fell by 0.6 mmol/mol for water.
Diastolic BP fell 1.7 mm Hg for diet drinks and fell 4.4 mm Hg for water
These differences were not clinically significant.
Both groups reported that hunger rose very slightly, but the difference was not significant.
So, what did we learn from this study? Over a two-year period, diet drinks offer an “effective alternative to sugar-sweetened drinks and perform equivalently to water.” Diet beverages, at least from this study published in the British Journal of Nutrition, do not deserve the negativity constantly given to them by detractors. Diet drinks are no more likely to cause weight gain, high cholesterol, and elevated A1C than plain old tap water.
Reference: Water or diet drinks? Weight loss held up either way. medscape.com 2026 October 6.
