Actually, a lot of people want to try it. The diet is already very popular in the United Kingdom.

Shohreh Jamalabadi-Majidi, clinical research coordinator, said she’s received an overwhelming number of requests to participate in the study, especially from women, and there’s a long waiting list.

Fontana said he believes the study is so popular because people are excited the diet only affects their eating habits for a few days a week. Still, a few people have dropped out because they can’t handle the changes.

On fast days, participants are instructed to eat only non-starchy vegetables. They can have one large portion in the evening or two smaller portions, for lunch and dinner. If they make a salad, they may have up to two tablespoons of olive oil a day, which are 100 calories each, and as much vinegar as they want.

“At the beginning, it can be difficult because people, especially in the U.S., they think they are always hungry, and they want to have always something in their hand to drink or to eat, but I think it’s psychological,” he said.

Yet for the most part, study participants have successfully stayed in the program. Obert said the majority complete more than 85 percent of fasts in a month.