The study, published online and scheduled to appear in the March 2012 print issue of The American Journal of Clinical Nutrition, compared weight loss for 318 overweight or obese people, who were divided into three groups: those who switched from calorie-laden beverages to diet soft drinks; those who switched to water; and those who were not counseled to change beverages but received general information about healthy choices that could lead to weight loss. All three groups attended monthly group sessions and had access to a group-specific website for six months.
"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," said study author Deborah Tate, PhD, associate professor of nutrition and of health behavior and health education at the UNC Gillings School of Global Public Health and member of the UNC Lineberger Comprehensive Cancer Center. "If this were done on a large scale, it could significantly reduce the increasing public health problem of obesity."
Tate and colleagues undertook the study to provide scientific evidence of whether eliminating calories from beverages is an effective weight loss tool that health-care providers and nutritional counselors could recommend. The study, known as CHOICE, or Choosing Healthy Options Consciously Everyday, is believed to be the first randomized controlled trial using noncaloric beverage substitution alone as the primary weight loss strategy in overweight adults.
"It does help," Tate said. "We learned that both water and diet sodas have some benefits, but they may be different. People who really like the sweet flavor or carbonation or caffeine of sodas may be more likely to stick with the change if they are drinking diet sodas as opposed to water only, but drinking water was associated with some other important health improvements like reduced blood sugar."
All three groups experienced small reductions in weight and waist circumference during the six-month study.
However, people who switched to calorie-free beverages were twice as likely to lose 5 percent or more of their body weight than those who were not counseled to change beverages. People in the group who drank mostly water had lower fasting glucose levels and better hydration levels than the control group.
Tate said that that percentage of weight loss and lower blood sugar levels were important because they are associated with clinical improvements in risk factors for obesity-related chronic diseases.
The study also noted that while participants' weight loss was less than reductions observed in more intensive, clinic-based behavioral lifestyle modification programs, the UNC study required minimal self-monitoring and prompted people to change just one aspect of their diets (beverages) - an approach consistent with other findings recommending small but potentially more sustainable lifestyle changes that people can make to improve their 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."
Other study coauthors were W.R. Kenan, Jr. Distinguished Professor of nutrition Barry M. Popkin, PhD, and AICR/WCRF Distinguished Professor of nutrition and epidemiology June Stevens, PhD; Gabrielle Turner-McGrievy, PhD, and Elizabeth Lyons, PhD, postdoctoral fellows at UNC at the time of the study who are now assistant professors at the University of South Carolina and the University of Texas Medical Branch at Galveston, respectively; Xiaoshan Wang, doctoral student in the biostatistics department; and Molly Diamond, Karen Erickson and Kristen Polzien, PhD, research staff at the UNC weight research program and UNC Lineberger Comprehensive Cancer Center.
The study was funded by Nestle Waters, U.S.A., but the company had no involvement in the study's design, conduct or preparation and review of the published paper.
The study is available online. A subscription is required.