People want to lose fat, gain muscle, and not spend a lot of time doing it. An easy way to accomplish this is... There is no easy way. The quickest and most effective way to lose fat and increase muscle is through High-Intensity Interval Training (HIIT). HIIT is based on short, intense burst of full capacity exercise followed by low activity or rest in intervals. The more intense the exercise, the less you do. The idea that aerobic exercise burns fat is phasing out. Although it does improve aerobic capacity; a study from The Cochrane Collaboration found moderate, aerobic activity to produce negligible weight loss.