you are right, but with this method the body is going to go to starvation phase(,it is a mechanism in body when the amount of calorie that your body gets is low ,your body thinks 'this is it, I have to adapt myself with the new situation' ). this is where your metabolism decreases and the calorie you burn gets even with the calorie you receive. the solution is that you get calorie but you burn it as well, you can not get in a good shape(you might get thinner but definitely not fitter ) without exercising
unfortunately being in a shape takes some efforts :/