An exercise programs to reduce abdominal visceral and subcutaneous fat in overweight and obese adults: A systematic review and meta-analysis of randomized controlled trials.

Background: Evidence that exercise reduces abdominal fat is ambiguous, so our review used a meta-analysis to evaluate the effects of differences among exercise programs.

Method: The inclusion criteria (population, intervention, comparison, and outcome [PICO]) were adults with overweight or obesity, the intervention group performed prolonged exercise and was compared to the control group that did not exercise, and both abdominal visceral fat area (VFA, cm²) and subcutaneous fat area (SFA, cm²) were measured as outcome. These fat areas were converted from absolute (cm²) to relative values (%). The mean differences (MDs) in abdominal VFA and SFA were calculated for each study.

Results: Twelve studies (591 subjects) were included in the analysis. Pooled MDs in abdominal VFA and SFA decreased significantly (-7.1 % and -9.1 %, respectively). The results of meta-regression analyses indicated that MDs in abdominal VFA (%) and SFA (%) were significantly associated with exercise intensity (metabolic equivalents [METs]) and baseline mean body mass index (BMI [kg/m²]). When the baseline BMI was 25 kg/m², meta-regression equations of abdominal VFA and SFA were γ= -3.1x + 13.3 and γ= -1.6x -4.3, respectively; when it was 30 kg/m², meta-regression equations of abdominal VFA and SFA were γ= -3.1x + 16.3 and γ= -1.6x + 2.2, respectively (γ, MD in abdominal fat and x, METs).

Conclusion: With an increase in exercise intensity, the abdominal VFA may decrease slightly more than the abdominal SFA. In addition, to equally reduce both abdominal VFA and SFA, overweight or obese people may need to exercise at a high intensity.