3. They make you eat more … fruit and veg
(Granted, some of the diets don’t include fruits, but those ones require even more veggie intake).
If you’re not getting a SUBSTANTIAL number of your daily calories from fruits and veggies you’re on a losing wicket. You’re not getting the right amounts of vitamins or minerals and probably not enough fibre either. Fruits and veggies are also relatively low in calories for the amount of food you eat, so instead of a 200g steak you could eat three platefuls of roasted veg.
Good deal if you like to eat a lot.