Do I need to exercise to lose weight?

You do not need to exercise to lose weight. You must exercise to maintain weight lost

As your dietary caloric intake goes down, the metabolic rate will also go down. If you did not exercise, as you go back on normal caloric intake, the threshold where the body determines to save extra calories as fat also gets lowered. This is the main reason why so many people gain more weight after they go off the diet.

The physical activity has two benefits: spend energy, and maintain metabolism. It is necessary to exercise to increase and maintain higher metabolic rate.