The Dumbbell Diet
To slim down and shape up, should you focus on losing inches or losing pounds? The scale cannot differentiate between fat pounds and muscle pounds, so while your scale weight may not budge as you lose body fat and gain lean muscle, the proof will be in the fit of your clothing. Your weight is composed of two separate elements: fat and lean body mass (muscle, bone, organs, and fluids).
Body composition is the "quality" of your weight as opposed to the "quantity" of your weight as measured by the scale. You can gauge your body-fat status roughly by the fit of a favorite pair of jeans. One pound of fat takes up more space than one pound of muscle, so as you lose fat you literally shrink. (Think of meat on display at the butcher's: a 3-pound roast is small compared to 3 pounds of fat).
Some people who appear to be lean and are of normal weight according to the charts can be qualitatively measured as over fat or "skinny fat." For example, a 20-year-old woman who does not lift weights will gain about five pounds of fat and lose five pounds of muscle by the time she's 50. This means that even if you maintain your scale weight perfectly over time, subtle changes are occurring in your body composition that can affect your health and appearance.
Lifting weights will sculpt the contours of your body. You will have a flatter belly, shapelier arms, firmer legs, and you'll look great in a little black dress. But body composition and body shape are about more than just looking good: they are also closely related to your health. With optimal body composition, including a high ratio of lean body mass to fat, you minimize your risk of developing diseases that are related to obesity, like heart disease, diabetes, osteoarthritis, gout, and some cancers.
Weight loss from exercise is primarily fat loss. As you exercise regularly, you will reduce fat stores from the whole body, and you will develop leaner, toned muscles instead. The gain in lean muscle tissue and loss of excess fat will result in trimmer contours and smaller circumferences regardless of the number of pounds lost.