Excessive Consumption of Diet Soda and Eating Disorders

Americans drink 4 billion gallons of diet soda a year (Boston Globe, April 11, 2013), and many studies are now underway to investigate possible unhealthy side effects of these diet drinks. Research continues into possible elevated risk of bone loss, fractures, and dental caries, and the possibility that the drinks’ phosphate and artificial sweeteners and coloring may exacerbate preexisting conditions. Individuals with eating disorders are among the groups that drink the most diet soda each day.

Why do people with eating disorders consume so much diet soda? Drs. Tiffany A. Brown and Pamela Keel, of Florida State University investigated some of the possible factors in a group of 240 individuals with lifetime eating disorders and 157 controls with no history of eating disorders (Eat Disord. 2013; 21:265).

According to the authors, three possible explanations for excessive intake of diet soda among persons with eating disorders are increased appetitive drive, increased concern about gaining weight, and overvaluation of weight and shape. Drs. Brown and Keel’s study sought to answer three questions: (1) do people with eating disorders really consume more diet soda than controls; (2) does consumption of diet sodas differ by the individual DSM-5 diagnoses of anorexia nervosa, bulimia nervosa, and eating disorders not otherwise specified (AN, BN, and EDNOS); and, finally, what effects do appetitive drive and weight/shape concerns have on diet soda intake?

The first stage of this two-stage study included completing a short questionnaire about the amount of soda, diet or otherwise, consumed each day and completion of the Eating Disorder Inventory (EDI). The Bulimia scale on the EDI reflects the behavioral portion of appetitive drive, or tendency toward overconsumption of food. The Drive for Thinness subscale was used as a proxy for weight concerns. In the second stage of the study, the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-1) was used to assess lifetime eating disorders. The investigators included all sections in the AN section regardless of the participant’s response to the item regarding low weight. Questions about the frequencies of binge-eating and purging behaviors were coded, regardless of whether they met the threshold of twice per week per week for 3 months—this approach allowed the researchers to capture sub-threshold forms of DSM-IV-defined AN and BN relegated to full threshold diagnoses in the DSM-5.

Those with eating disorders drank more diet soda than did controls

Individuals with a lifetime eating disorder, specifically those with BN, consumed more diet soda per than did controls. And, all individuals with a lifetime eating disorder consumed more diet soda per day (mean: 4.48 cans) than did controls (mean: 2.48 cans per day). Individuals with BN drank an average of 6.9 cans of diet soda per day.

Symptoms associated with appetitive drive or weight concerns were associated with increased intake of diet soda; fear of gaining weight or becoming fat had a medium-sized effect. Increases in Drive for Thinness were associated with increased intake of diet soda; no relationship was found for the bulimia subscale but there was a significant interaction between Bulimia and Drive for Thinness.

Implications for clinicians

The authors report that their findings have some potential implications for clinical practice. For example, they reference prior work suggesting that in patients with AN, consuming higher-energy-dense foods predicted treatment success (Am J Clin Nutr. 2008; 87:810). The authors suggest this may be especially true for patients with BN. For these patients, excessive intake of diet soda may not only exacerbate medical problems, but may maintain or contribute to dysregulated eating patterns.

Drs. Brown and Keel conclude that patients with BN may use diet sodas as a way to satiate their appetitive drive or to “fill up” without adding calories. Thus, as the authors had theorized, a combination of high appetitive drive and high weight concern among patients with BN may indeed underlie excessive consumption of diet sodas.