Proteins are needed to build and repair the body and these are your friend to make the lean body.
These help to burn the fats, even the stored fats and convert them into energy.
These are extremely important after exercises as they repair the wear n tear of muscle tissues which happen during exercise.
But NO high protein diets. As suggested by some dieticians are not good for health as these put extra load to kidney and can even cause kidney damage. Also too much of fat does not get stored for future use but coverts to fat.
Proteins in medium quantity are must
Can read more at https://www.webmd.com/men/features/benefits-protein#1