A number of supplements marketed for weight loss and improved athletic performance contain a synthetic compound that is similar to the drug amphetamine, and that compound has not been tested in people, according to a new study.

What’s more, the Food and Drug Administration has known about the presence of this drug in supplements for two years, but still has not warned consumers about the issue or acted to take the supplements off the market, according to the study.

The FDA “did a lot of hard work to figure out this brand-new designer stimulant was in supplements … and then failed to inform the public,” said Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School and co-author of the new study. “It’s inexplicable and inexcusable,” Cohen said.

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