Do Diet Sodas Really Help with Weight Loss?

By , Holly Wyatt, MD
One of the questions that I am often asked by my patients at the Anschutz Center for Health and Wellness is this: ''Can I drink diet soda and still lose weight?'' The follow-up question is usually: ''Is it true that diet beverages can make me feel hungrier?''
 
That’s when I know that they are seeing some of the same confusing headlines about diet beverages that I often see in the local and national news media, and even more frequently on the web.
 
What I love about my job is that I get to try to find answers to some of these puzzling nutrition questions. To that end, my colleagues and I just completed a study that asked the question: what effect do diet beverages have on weight loss? We were surprised by the answers, which makes me think that you may be, too. 
 
First, here’s what we did:  we recruited more than 300 people who wanted to lose weight and were already drinking diet beverages at least three times a week. We then randomly assigned them to one of two groups, and over 12 weeks, all of them received an identical diet and exercise regimen. The only difference? In one group, we asked them to give up something they enjoyed -- drinking diet beverages – and agree to drink only water, and at least 24 ounces (or three cups) of it every day. In the other group, we allowed them to keep enjoying diet beverages, but asked that they consume at least 24 ounces (or two cans) per day. At 12 weeks, we ended this phase of the study and looked at the results. Since diet beverages and water have zero calories, we expected that both groups would likely lose about the same amount of weight.
 
The surprise? The diet beverage drinkers lost an average of 13 pounds during the 12 weeks—four pounds more than those in the group that drank water only.
 
We also learned that the diet beverage drinkers felt less hungry than their counterparts. And that more of them would lose five percent of their total body weight. And that their blood cholesterol levels would improve more than their counterparts. These were very significant findings and we published the first phase of our study in the journal Obesity.
 
Now, we are completing the second phase of the study, which will end in August. We want to see how both groups of dieters fare over the long term, and we plan to publish those results as well.
 
In the meantime, however, I have a better answer to give to my patients when they ask about diet sodas. Now I can tell them: ''Yes, if you’re trying to lose weight, you can still do so while enjoying diet beverages.''
 
I can also tell them that, according to our results, having diet beverages may make them feel a little less hungry and that, in turn, might help them stick with their goal of losing weight.   

This blog is brought to you by the American Beverage Association

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