Purpose: It is known that a preferential deposition of fat in the abdominal region is the obesity phenotype that conveys the greatest health risk. Although physical activity is commonly prescribed to reduce obesity, the influence of exercise-induced weight loss on abdominal fat is unclear. This review was undertaken to clarify whether abdominal fat is preferentially reduced consequent to weight loss induced by regular exercise.
Methods: A literature 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 controlled trails (RCT) wherein it was clear that exercise alone induced weight loss. For the four RCT within which regular exercise was not associated with weight 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 (approximately 3 cm) is observed in response to exercise-induced weight loss of about 3 kg. Without exception, these studies were not designed to determine whether abdominal obesity was preferentially reduced. Absent from the literature are RCT that employ imaging techniques (e.g., computerized tomography or magnetic resonance imaging) to determine whether exercise-induced weight loss is associated with reductions in either visceral or abdominal subcutaneous fat. However, 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.
Conclusion: There is insufficient evidence to determine whether exercise-induced weight loss is associated with reductions in abdominal fat. Clearly there is a need for carefully controlled studies wherein the primary aim is to determine the influence of regular exercise on total and abdominal adiposity.