In simplistic terms, calorie balance is THE most important part of the fat loss equation and has the largest effect on any diet outcome.
Generally all ‘fad diets’ work up to a point because they put you in to what’s called ‘a negative calorie state/balance’. It’s that simple, eat fewer calories than the body needs to perform its daily functions and you’ll lose weight.
It does get slightly more complicated than that if fat loss is your goal!