When Canadian snowboarder Ross Rebagliati tested positive for marijuana at the 1998 Olympics, he almost lost his gold medal. Rebagliati insisted that he hadn’t smoked weed since 1997, and must have inhaled second-hand smoke at a party. In the end, the IOC returned the hardware, saying it didn’t have the authority to strip him of it. But a new study might explain what happened. According to researchers at the University of Sydney, stress or exercise can cause “reintoxication.” In other words: athletes may test positive for cannabis, despite not having used the drug in a long time. As tests on rats revealed, because tetrahydrocannabinol (THC) is stored in fat cells, rapid weight loss can release it into the blood stream. The next step, they say, is to show the same results in humans.