This randomized 24-week clinical trial examined whether swapping diet beverages for water improves outcomes for women with type 2 diabetes participating in a structured weight-loss program. The study enrolled 81 overweight or obese women (BMI 27–35, ages 18–50) with type 2 diabetes who regularly consumed diet beverages and were treated with metformin only. After a two-week washout period avoiding artificial sweeteners, participants were randomized to one of two groups: either replace their usual post-lunch diet beverage with a 250 mL glass of water, or continue drinking a 250 mL diet beverage after lunch. This substitution was done once daily, five days per week, for the full 24 weeks, while both groups followed the same clinic-based, hypo-energetic weight-loss program.

 

The weight-loss program aimed for a 7–10% reduction in initial body weight over 24 weeks, using individualized meal plans, behavioral support (goal setting, self-monitoring, food diaries), and regular follow-up with a dietitian every two weeks to reinforce adherence. Physical activity was encouraged, with a gradual goal of reaching about 60 minutes of moderate activity five days per week. Outcomes were measured at baseline, 12 weeks, and 24 weeks, including weight and BMI (primary focus), waist circumference, fasting and post-challenge glucose measures, insulin and insulin resistance (HOMA-IR), HbA1c, and standard lipid panels.

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Both groups lost weight and improved metabolic measures over time, consistent with the effects of a comprehensive lifestyle program. However, replacing diet beverages with water produced a modest but statistically significant added benefit. Over 24 weeks, the water group lost more weight (about 6.4 kg vs 5.25 kg) and had a larger reduction in BMI. The water group also showed greater improvements in glycaemic control and insulin sensitivity, including larger decreases in fasting plasma glucose, fasting insulin, HOMA-IR, and 2-hour postprandial glucose. In contrast, the groups did not differ meaningfully in changes in waist circumference, lipid profiles, or HbA1c over the 24-week period.

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The study suggests the advantage of water may relate to better overall dietary adherence when artificial sweeteners are removed, potentially reducing cravings for sweet or energy-dense foods. Key limitations include the women-only sample, reliance on self-reported intake and compliance, lack of objective verification of total energy expenditure, and the narrow focus on a single daily beverage timing (after lunch).