Brooke Shields made the “grapefruit diet” famous. It includes 800 calories a day and lots of the pink citrus fruit.
The grapefruit diet may help you lose weight, but only because of severe calorie restriction, not because of any magical enzyme the fruits contain.
The diet plan limits calories to just 800 a day, comprised of eggs in the morning, grapefruit all day, and a small piece of meat with veggies for dinner.
That kind of undereating can cause you to shed muscle mass, slow your metabolism, and, in severe cases, lead to serious problems due to malnutrition. It can also be dangerous to people already at risk of eating disorders.
That said, grapefruit does have some benefits, like vitamin C and potassium. But it blocks a specific enzyme related to breaking down some drugs, which can mean your body gets a higher dose, so be cautious about mixing it with your meds.