I have spent some time collecting information about popular diets, including some pretty bizarre fad diets, and the most bizarre prize has to go to the tapeworm diet. The idea is to ingest a tapeworm, which then shares your gut and consumes some of your calories. I have no doubt you will also feel unwell and will eat less food too. Just the thought of it has put me off my food.
You can buy tapeworm eggs to ingest (really!), but if you are really desperate you could just try eating undercooked meat (I’m kidding). I am not surprised that some desperate people do actually try this extreme measure diet, but it is not at all recommended, it is dangerous, don’t do it, seriously.
Read more about the Tapeworm Diet.