Can diet drinks help with weight management?

Replacing diet beverages with water over 18 months leads to greater weight loss, improved glycaemic control, and higher diabetes remission in women with type 2 diabetes (T2D) and overweight or obesity. The benefits were sustained throughout the 18-month trial.

The 18-month weight management programme comprised two phases: Active weight loss intervention for 6 months (phase 1) and weight maintenance for 12 months (phase 2). Phase 1 involved a structured diet programme targeting 0.5–1 kg/week weight loss, with 60 min of activity 5 days a week and biweekly counselling. In phase 2, participants underwent monthly nutrition visits and group sessions, with adherence tracked through food and beverage intake logs and activity records.

Eighty-one adult women with T2D and obesity or overweight who usually consumed diet beverages were randomized 1:1 to either continue consuming 250 mL of diet beverages five days a week or substitute it with 250 mL of water after lunch. [ADA 2025, abstract 586-P]

Between baseline and the 18-month mark, water consumers had significantly greater weight change than those who continued drinking diet beverages (mean, -6.82 vs -4.85 kg; p<0.001), and a third (34.1 percent) of water drinkers achieved a ≥10-percent weight reduction vs only 2.5 percent of diet beverage consumers (p<0.0001).

The proportion of participants who achieved T2D remission (HbA_1c <6.5 percent or <48 mmol/mol) at 18 months was twofold greater in the water vs diet beverage group (90 percent vs 45 percent; odds ratio, 11.31, 95 percent confidence interval, 3.39–37.73; p<0.0001). Of note, 85 percent of participants in the water group have already achieved remission after phase 1; in the diet beverage group, only 27.5 percent achieved this outcome at 6 months.

Month 18 also saw significantly greater mean changes in BMI (-2.66 vs -1.89 kg/m²; p<0.001), waist circumference (-8 vs -7 cm; p=0.018), and triglyceride levels (-0.45 vs -0.34 mmol/L; p=0.005) with water vs diet beverage, as well as in glycaemic markers including HbA_1c (-1.33 percent vs -0.51 percent), fasting plasma glucose (-2 vs -1.15 mmol/L), 2-hour postprandial glucose (-1.77 vs -1.02 mmol/L), insulin (-5.88 vs -3.51 U/L), and homeostasis model assessment of insulin resistance (-3.51 vs -2.17; p<0.001 for all).

The water group also had greater reductions in energy intake (-477 vs -309 kcal; p=0.001) and carbohydrate intake (p=0.002) than the diet beverage group.

Water remains the optimal choice

The obesity epidemic is a major driver of the rising T2D incidence worldwide, the investigators noted. “Most individuals with T2D are overweight or obese; hence, weight reduction is a primary therapeutic target. A loss of ≥10 percent body weight has been strongly linked to diabetes remission.”

Diet beverages have been considered a suitable alternative to sugar-sweetened beverages. [Circulation 2007;116:480-488; Am J Clin Nutr 2014;100:765-777] However, evidence has shown a potential link between diet beverage intake and increased risk of T2D and obesity. [Adv Nutr 2023;14:710-717]

“Our findings provide clinical evidence supporting the general recommendation by nutritionists that water is the optimal beverage for promoting weight loss and improving glycaemic control in individuals with T2D,” said the researchers.

Water substitution was also linked to better adherence to dietary goals and larger reductions in energy and carbohydrate intake, they added. The researchers called for further trials to validate the results and shape diabetes management guidelines.