Spot reduction refers to the belief, long viewed as a myth, that fat can be targeted for reduction from a specific
area of the body. This is a common view, although many people believe that view is misguided, that it is possible to achieve spot reduction through exercise of specific muscles in the desired area, such as exercising the abdominal muscles in an effort to lose weight in or around one's midsection. Advertisers exploit this concept when advertising
However, many fitness experts do not believe it is possible to reduce fat in one area by exercising that body part alone. Instead, fat is lost from the entire body as a result of diet and regular exercise. Muscle growth in the abdominal region does not reduce fat in that region. Instead, being on a caloric deficit is recommended for reducing abdominal fat.
The misunderstanding may be attributed to the firming and shaping effect of muscle hypertrophy. When additional muscle is built, it takes up new space which can briefly compress subdermal fat against the skin until the skin adapts, a larger bulging muscle shape is also more easily seen through the layer of fat on top of it. This can give the illusion of fat being reduced when it has not. For example, triceps hypertrophy firming the back of the arm.
A 2006 study published in the American Journal of Physiology seemed to indicate that spot reduction may be possible, although the measured results were trivial. In the study, conducted at the University of Copenhagen (Denmark), scientists had male subjects perform single-leg extensions with light weight for 30 consecutive minutes. The researchers then measured the amount of blood flow to the subjects' subcutaneous fat cells in both the exercising and resting thighs, as well as the amount of lipolysis from those fat cells. The scientists observed increases in blood flow and lipolysis in the exercising leg when compared to the resting leg. The study suggested that during exercise, body fat is preferentially used from the area being trained, but at a magnitude that has
little to no practical significance.