TUESDAY, Feb. 14 (HealthDay News) -- People who drank water or diet beverages instead of calorie-laden drinks lost 4 to 5 pounds over half a year, according to new research.

The study included 318 overweight or obese people divided into three groups: those who switched to water from high-calorie beverages; those who switched to diet soft drinks; and those who weren't advised to change beverages but were given general information about healthy choices that could help them lose weight (the control group).

Over the six-month study, all three groups had small reductions in weight and waist circumference. But those who switched to calorie-free beverages were twice as likely to lose 5 percent or more of their body weight than those in the control group.

In addition, the investigators found that people who drank mostly water had lower fasting glucose levels and better hydration levels than those in the control group.

Percentage of weight loss and lower blood-sugar levels are important because they're associated with improvements in risk factors for obesity-related chronic diseases, according to study author Deborah Tate, an associate professor of nutrition and of health behavior at the University of North Carolina Gillings School of Global Public Health and member of the Lineberger Comprehensive Cancer Center.

"Substituting noncaloric beverages -- whether it's water, diet soft drinks or something else -- can be a clear and simple change for people who want to lose or maintain weight," she said in a university news release. "If this were done on a large scale, it could significantly reduce the increasing public health problem of obesity."

The study appears online and in the March print issue of the American Journal of Clinical Nutrition.

Weight loss among the participants in this study was less than that seen in more intensive, clinic-based behavioral lifestyle modification programs, the researchers said. However, they noted that asking people to change just one part of their diet (in this case, beverages) is consistent with previous findings recommending small but potentially more sustainable lifestyle changes to improve health.

"Substituting specific foods or beverages that provide a substantial portion of daily calories may be a useful strategy for modest weight loss or weight gain prevention," Tate said. "Beverages may be ideal targets, but keep in mind, the strategy will only work if the person doesn't make up for the lost calories some other way."

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases explains how to choose a safe and successful weight-loss program.