Fat loss and muscle gain must go together to achieve leanness. Dieting alone won’t work! If you lose fat by dieting without simultaneously gaining muscle by exercising, you might end up actually gaining weight. As you lose fat by dieting alone, you can also lose some of the muscle that the body used to support the extra fat. As a result, the body’s resting metabolic rate (RMR) diminishes, so you burn fewer calories as your dieting body clicks into anti-starvation, fat-storage mode. Yet, if you increase muscle at the same rate you lose fat, you keep the RMR revved up and can even increase it to continue burning rather than storing calories.