Working out is typically performed with specific goals for how you want your body to look once you are in top shape. Each person may have a different part of her body that is particularly stubborn and requires more attention than others. If your legs are your problem area, it can be difficult to tell if you're building muscle mass or fat. This is especially true in the early stages of fitness, when muscle mass is covered by a layer of fat tissue.
Men and women are distinctly different in how they metabolize and store excess fat, explains exercise physiologist Len Kravitz of the University of New Mexico in the online publication "Gender Difference in Fat Metabolism." In individuals with gynoid -- or pear-shaped -- bodies, excess fat is more likely to be distributed in the legs and hips than around the abdomen. The gynoid body type is more common among females. In contrast, most males who carry excess fat have android -- or apple -- body types, in which fat is more likely to be stored in and around the abdomen.
Your body type is a measure of your metabolism and how your body utilizes and stores fat. The endomorph body, in contrast to the ectomorph and mesomorph, is efficient in storing fat deposits, giving them a rounded or soft appearance. Despite this, the website Muscle and Strength explains in their online guide "Your Body Type," that endomorphs also tend to have very strong lower body muscles. These muscles are some of the largest in your body, meaning that making them physically fit encourages your metabolic rate to increase. Endomorphs also have a tendency to put fat on more easily than muscle, making it more likely that the untrained legs contain disproportionately more fat.
Fat calipers, according to Sequoia Fitness in their guide to using this tool, provides you with an overall measurement that represents your percentage of body fat. You can find a fat caliper at your local sporting goods store or borrow one at your local gym. Although the measurement of body fat is comprehensive for your whole body, the knowledge of your body type or body shape can help you determine where your legs are muscular or have fat deposits over the muscle.
An easy way to evaluate whether your legs are mostly muscle or fat is to look at them in a mirror. Signs that your legs are muscular include defined lines of separation between the muscles of the hamstrings, quadriceps and calves. Flexing the muscles and seeing these lines indicates that you may have some excess fat that lies over your leg muscles. If your legs aren't toned, this approach may not be as effective, because you won't have the muscular definition. Cellulite, which is the dimpling of your skin that indicates fat deposits, is characteristic of excess fat on your legs.