Muscles are where energy is released, power is produced, and where movement originates. Because the condition of our engine has a lot to do with the way we look, feel, and function, strong muscles are very advantageous. That how much will waste away or atrophy. This lowers your metabolic rate. If there is no corresponding reduction in caloric intake, the result is a gradual gain of body fat.
Excess fat is unhealthy - and, to most people, unappealing.
More muscle and less fat improves most people's physiques. Strength training is the best way to simultaneously increase muscle and decrease fat. There's a common misconception that to shed body fat you must do aerobics. Doing aerobics, it is thought, burns fat as fuel, while strength training utilizes carbohydrate energy. What's not often recognized is that it really doesn't matter what type of fuel your body is using.