Upon first seeing this old turn of the century diet ad, I thought, “wow, interesting - its funny that people accepted this as a weight-loss technique at one time.” Then I found this paragraph on a current dieting website and now I’m kinda freaked out:

The first thing that dieters must know is that tapeworm importing or selling is illegal in the United States. Consumers who want to attempt this diet will have to travel to Mexico to do so. Once you arrive at the location for treatment (quite possibly a slaughterhouse), you will be provided with beef tapeworm cysts that have been identified microscopically as such. The reason this is so important is that some cows may have been infected with a pig tapeworm, which is much more dangerous than the parasites found in cows. The cysts are consumed, and a tapeworm will grow inside the digestive tract. Dieters can expect to lose one to two pounds a week as long as the tapeworm is inside. Once the target weight loss is reached, an antibiotic is given and the tapeworm is killed and expelled.