New research once again brings the ongoing debate on whether or not “diet” beverages aid in weight loss or deter from it to the forefront.
Published in the journal Obesity and fully funded by the American Beverage Association, the study split 300 men and women into two groups: Half drank at least 24 fluid ounces of diet drinks (qualified as having less than 5 calories per 8 ounce-serving, being pre-mixed, and containing non-nutritive sweetener) each day, while the other half drank at least 24 fluid ounces of water daily but could not drink diet beverages (they could, however, eat foods like yogurt, pudding, and Jell-O that contained artificial sweeteners).
During the 12-week study, both groups received a comprehensive cognitive-behavioral weight loss intervention called the Colorado Weigh. They met weekly with either a psychologist or registered dietitian, and were educated about many weight-loss topics including portion sizes and food label reading. Each participant was given an individualized daily calorie target based on their resting metabolic rate to promote a loss of 1 to 2 pounds a week.
At the end of the study, diet beverage drinkers lost 13 pounds compared with 9 pounds for those who abstained from these drinks.
The researchers aren't sure why the diet drinkers lost more weight, though they note that because eligible subjects assigned to that group were already diet beverage drinkers, they did not require as great of a behavior change as the water group did. I think this is a very big factor in the results. Whenever somebody has to make a big change in his or her diet to lose weight, it makes it more difficult. Perhaps the water group ended up compensating in other ways, i.e. sweetened beverages or more artificial sweetened food, which are not in any way calorie free. As far as I could assess from the study, participants didn't keep a food journal, so I am really curious as to their total daily intake apart from beverages.
Also it is important to remember that this study is not suggesting that you should start drinking diet beverages for weight loss, but rather if you already drink them, then it shouldn’t prevent any loss. Since 12 weeks is a short time to assess real behavior change, I am most anxious to see the author’s next published results on the 9-month maintenance phase that is presently underway. Which group actually keeps the weight loss off honestly is the most important. In the meanwhile I will continue to recommend plain, old water for weight loss. Zero calories and nothing added—no debate needed.