A tax on over-the-counter diet pills could be an effective public-health strategy to discourage teenagers from purchasing the dangerous and “useless junk,” according to a first-of-its-kind study coauthored by economics professor Nathan Tefft.

The $66 billion diet industry faces few regulations, explain Tefft and co-author S. Bryn Austin in their blog post for the National Eating Disorders Association. Yet “what the diet industry does not want you to know…is that most of what they sell is at best useless junk — and that could not be truer than for diet pills,” say the researchers.

Nathan Tefft, associate professor of economics. (Sarah Crosby/Bates College)

Weight-loss products are particularly dangerous, with 23,000 annual emergency room visits attributable to dietary supplements. Among girls and women, fully a third of these ER visits are caused by weight-loss supplements — yet teenagers, especially, should not take diet pills.

So what measures can policymakers take to keep diet pills out of the hands of teens? Based on the fact that taxes on cigarettes have been “one of the most effective strategies to date to drive down teen smoking,” the researchers looked at whether “taxing diet pills might be a solution.”

The answer is a resounding “yes.” A 20 percent tax on diet pills could lead to a 5.2 percent decrease in overall purchases — and, importantly, a 17.5 percent decrease among households with teenagers.

“That may not sound like a lot,” wrote Austin and Tefft, “but there are over 126 million households in the U.S., and roughly one in five of them purchase these products, so a 5 percent decrease across millions of American households is a lot of diet pills not finding their way into the medicine cabinets in people’s homes.”

Associate Professor of Economics Nathan Tefft leads a class. (Josh Kuckens/Bates College)

The study will be published in a forthcoming issue of the journal Preventive Medicine.

Tefft, who studies the economics of public health issues and has examined the effects of taxation on other products, conducted the study in collaboration with Austin, director of the Strategic Training Initiative to Prevent Eating Disorders at Harvard’s T.H. Chan School of Public Health and Boston Children’s Hospital; and with Selena Hua Liu of the Department of Nutrition at Simmons College.