Reducing muscle size is much easier than increasing muscle size and requires a lot less work. Although it may seem a bit unconventional, the desire to reduce muscle size is more common than you may think. Athletic women, for example, may wish to reduce the size of muscular thighs to achieve a slimmer look. It is possible to reduce muscle size by simply becoming sedentary, but that is not a very healthful approach. Whether you want to reduce a certain body part or size down your entire body, you can safely and healthfully reduce muscle size.