Running can be an efficient way to lose fat and tone the muscles of your lower body. In contrast to other forms of exercise, like walking or bodybuilding, running encourages your body to burn off fat calories quickly. If you're trying to lose body fat, running can encourage your body to burn as much as 295 calories in an hour. Unfortunately, this fat loss is generalized and not targeted to specific areas of your body. Running can therefore lead to a decrease in the size of your breasts. The female breast is composed of several types of tissue. The Mayo Clinic explains that aside from fat cells, which provide padding and insulation for the mammary glands, the breast also contains arteries and capillaries. The amount of fat you have in your breasts is largely determined by heredity but is also influenced by age and hormonal fluctuations. There is no muscle tissue found in your breasts, but muscles do lie directly under the breasts against the surface of your ribcage. Running is a type of aerobic activity, which means your body requires oxygen in order to accomplish the exercise. The oxygen provides your muscles with the ability to push past their typical ability into a zone where you burn fat for energy. As a result, your body draws fat from the stores throughout your body, including your breasts. The amount of fat lost during and after an aerobic activity is influenced by your age, height, weight and level of fitness. A pound of fat is the equivalent of 3,500 calories, regardless of where that fat is stored in your body. In contrast to anaerobic activity such as bodybuilding, aerobic exercise can help you lose fat faster. The fat stored in your breasts and other areas is used to provide fuel while running, and a woman who weighs approximately 150 pounds will burn nearly 300 calories by running for an hour. Running for an hour a day can lead to fat loss of more than half a pound each week for a 150-pound woman, assuming no other changes in diet or activity. Running can not only lead to a reduction in fat stores in breast tissue, it can also lead to changes in the shape and tone of your breasts. This is even more likely to occur as you age and your skin becomes less elastic. In order to minimize the effects of fat loss from your breasts, combine aerobic activity with resistance exercises. These exercises, which include weight training, can increase the tone, size and support of the muscles that lie under and around your breasts. Source
