The claim that artificial sweeteners might contribute to obesity is one we have seen many times in the past. The newest study on the subject is a research article just published in the Journal of the American Geriatrics Society which evaluated the possibility of a relationship between the consumption of diet soda and increasing waist circumference (WC) in older Americans (i.e., over 65 years old). Waist circumference is used as an index of abdominal obesity the type that is closely linked to various metabolic disorders and some cardiovascular risks.
The authors of the study, led by Sharon P.S. Fowler, MPH from the University of Texas Health Science Center in San Antonio, and colleagues examined the diet soda consumption and changes in WC between 1992 and 2004 among nearly 750 participants including both Mexican-Americans and Caucasians. Initially, WC, height and weight were measured and diet soda intake (DSI) was assessed from self-reports. These measures were re-assessed three times during the course of the investigation.
The investigators found that as DSI increased, so did WC. The increase in WC was 0.80 inches for non-users, 1.8 inches for occasional users, and 3.2 inches for daily users. Thus there was a clear dose-response trend in the data. But what does it mean?
As ACSH s Dr. Ruth Kava explains, Even though some media articles seem to just buy into the authors theory that diet sodas cause obesity, this conclusion can t be drawn from this observational type of study. First, it is possible that the participants who were consuming the most diet soda were compensating for the decreased calories in such drinks by consuming more food. But calorie consumption wasn t measured in this investigation, so it s impossible to tell if this is true. Further, self-reported data are notoriously unreliable, and it would be important to have some measure of reliability. Importantly, there is no biologically-plausible hypothesis to explain how diet soda, or anything in them, might promote weight gain. This is clearly a case of the authors, in their quest to impugn diet soda, confusing cause and effect. The take-home message is that if there is any link between diet soda and putting on additional fat in later years, the explanation is most likely that people who have a tendency to gain weight also have a tendency to drink diet sodas.