Observational Study on Diet Soda and Waist Circumference Does Not Establish Causal Link

Contact Info: 

Contact Matt Raymond (raymond@ific.org) or Laura Kubitz (kubitz@fic.org) at 202-296-6540.

A new study, “Diet Soda Intake Is Associated with Long-Term Increases in Waist Circumference in a Biethnic Cohort of Older Adults: The San Antonio Longitudinal Study of Aging (SALSA),” does not establish a causal link between low-calorie sweetener consumption and increasing waistlines in older adults, and should be interpreted cautiously.

Among many limitations of the study design and related findings:

  • Observational studies are unable to establish cause-and-effect.
  • Weight gain and other health conditions such as cardiovascular disease are known factors may be associated with aging.
  • Study subjects were asked to self-report what they consumed, which introduces recall bias.
  • The researchers failed to adjust for total calorie intake, which would impact the results.

Additionally, the study of 749 adults aged 65 and older spanned more than 12 years, with just 50 percent of the original subjects living through the end of the study. With the newest data being more than 10 years old at the time of publication and much having changed since then with respect to low-calorie sweetener availability and consumption, these findings may be limited in their relevance to consumers today.

“This study should not garner any reason for concern given the vast limitations of the study and the fact that clinical studies have shown low-calorie sweeteners to be effective tools for weight management, when used in place of caloric sweeteners and when consumed as part of a healthful diet and with regular physical activity,” said Marianne Smith-Edge, MS, RD, LD, FADA, Senior Vice President, Nutrition and Food Safety, International Food Information Council.

For more information on evaluating scientific research, refer to IFIC Foundation’s Evaluating Evidence brochure, which provides guidance on important questions to ask when looking at a new study and its relevance to the broader body of scientific literature.

Additional Resources on Low Calorie Sweeteners: