In April 2015, the US Right to Know (US RTK), a non-profit organization that reports on food industry issues on behalf of consumers, sent a letter to the Federal Trade Commission (FTC) and a citizen petition to the Food and Drug Administration (FDA) with requests to investigate diet soda manufacturers for misbranding and deceptive advertising on the grounds that the “diet” products contain artificial sweeteners that US RTK alleges actually contribute to weight gain.

The request for FTC investigation states that the soft drink companies deceptively imply that artificially sweetened beverages contribute to weight loss rather than weight gain and requests that the FTC prohibit the companies from using the term “diet” in advertising such products. US RTK argued that representing that such products are “diet” is likely to mislead reasonable consumers, and that consumers will rely on the claims to their detriment.

In the FDA citizen petition, US RTK requests that FDA 1) issue a warning letter for use of the term “diet” as being false and misleading, and 2) investigate the use of the term “diet” (and other terms implying weight loss in other artificially sweetened products) to determine if the product brand names or labels are misbranded.

In both requests, US RTK stated that the implied claim that consuming diet soft drinks will assist in weight loss is false. The request and petition cite four reviews of scientific literature on artificial sweeteners that suggest that they do not contribute to weight loss, but rather lead to weight gain. Additionally, US RTK pointed to epidemiological evidence, interventional studies, and animal studies that suggest that artificial sweeteners implicated weight gain. The requests also cite two industry studies that did not find a link between artificial sweeteners and weight gain.

FTC declined to comment on the issue, responding in a letter that it would not take action, although it reserved the right to take further action as the public interest may require.

FDA provided an interim response to the citizen petition, stating that it has not yet reached a decision regarding US RTK’s requests. It is unclear at this time whether FDA will also stay any action against the diet soda manufacturers.

It seems that the two regulatory agencies are not willing to expend resources reviewing the controversial topic, despite the scientific support provided. While action is unlikely, the requests reflect an increasing public focus upon such claims and their underlying validity. In the absence of government action, more civil class action litigation over such questions is likely on the horizon.