Nowadays in this busy life ,peoples are least active .So walking is a good cardio activity towards work or vice versa to be active in our daily life. Brisk walking for minimum of 30 min will help reducing our fat % and burn calories. But it wont work out to shape up your body and improving BMR. It can be improved only by doing resistance training exercises like Crunches, Reverse crunches, Abbs Cycling, Thigh raises, Leg pushs, Shalabhasna , Push ups , etc. Doing these exercises atleast on week ends will help keeping you fit and shape up your body.