I think that as a policy matter it is better for society to create an exception to the rule of complete bodily autonomy, mostly because of harm to people around the user. I don’t think users should get jail time but some penalties are ok. This is partly based on personal experience and partially on stats like increasing DUI rates post cannabis legalization. I don’t see much of a slippery slope argument to be made from psychoactive drugs to carbs, which are a basic nutrient anyone can find anywhere.