What is the best way to get nice body shape and loose weight ?workout or dieting?

You need both to lose and maintain weight. If you only workout you will just maintain your weight and if you only diet you will gain the weight back.

You CAN lose weight just by dieting but it will take longer and you will gain it back if you don't make permanent changes to your eating habits... Exercise is an important component and not just because in conjunction with a diet for weight loss it is more effective... but because most of us really don't get enough exercise to begin with and its important to your health in many ways.