Is abdominal fat preferentially reduced in response to exercise-induced weight loss?

Purpose: It is known that a preferential deposition of fat in the abdominal region is the obesity phenotype that conveys the greatest health risk. Alt hough physical activity is commonly prescribed to reduce obesity, the influ ence of exercise-induced weight loss on abdominal fat is unclear. This revi ew was undertaken to clarify whether abdominal fat is preferentially reduce d consequent to weight loss induced by regular exercise. Methods: A literat ure search (Medline, 1966-1998) was performed using appropriate keywords to identify studies reporting changes in both whole body and abdominal fat in response to exercise. Results: At present there are no randomized controll ed trails (RCT) wherein it was clear that exercise alone induced weight los s. For the four RCT within which regular exercise was not associated with w eight loss, abdominal fat measured by waist circumference was unchanged. A similar trend is observed for the nonrandomized studies. Abdominal obesity as measured by waist circumference is unchanged for those studies reporting no loss in weight or fat; however, a modest reduction (similar to 3 cm) is observed in response to exercise-induced weight loss of about 3 kg. Withou t exception, these studies were not designed to determine whether abdominal obesity was preferentially reduced. Absent from the literature are RCT tha t employ imaging techniques (e.g., computerized tomography or magnetic reso nance imaging) to determine whether exercise-induced weight loss is associa ted with reductions in either visceral or abdominal subcutaneous fat. Howev er, the findings from four nonrandomized or controlled studies report that exercise with or without weight loss is associated with reductions in both visceral and subcutaneous fat. Conclusions: There is insufficient evidence to determine whether exercise-induced weight loss is associated with reduct ions in abdominal fat. Clearly there is a need for carefully controlled stu dies wherein the primary aim is to determine the influence of regular exerc ise on total and abdominal adiposity.