This is kind of a loaded question. Yes, you need to exercise to be healthy. No, you don’t have to exercise to lose weight. However, doing so will drastically cut the amount of time you spend losing weight. Exercising boosts metabolism, prevents injury, strengthens the immune, cardiovascular and respiratory systems, along with making you feel better (chemically, emotionally, hormonally). Although higher intensity resistance training (lifting weights) would be best, even moderate intensity exercise (like walking or biking) has been shown to have immense benefits.