The effect of exercise on visceral fat in type 2 diabetes

Introduction: It is widely acknowledged that obesity increases cardiovascular and metabolic morbidity and mortality, and that visceral adipose tissue (VAT) is a major contributor to adverse cardiometabolic health in obesity-related type 2 diabetes. Although it is increasingly recognised that regular exercise has little effect on long-term weight loss, numerous investigations have reported a multiplicity of other benefits, including a reduction in VAT. A systematic review and meta-analysis was performed to assess the efficacy of exercise interventions on VAT area/volume in overweight and obese adults with type 2 diabetes. Methods: Relevant databases were searched to February 2016. Inclusion criteria included randomised controlled studies in which aerobic exercise training (AEx) or progressive resistance training (PRT) was used exclusively, or in combination for a minimum period of 4 weeks. Studies were selected if computed tomography or magnetic resonance imagining were used for the quantification of VAT area/volume pre- and post-intervention. Results: The original search included 7,588 studies, of which 15 were selected based on the eligibility criteria. After the removal of outliers, a significant pooled effect size (ES) was found for the comparison between AEx and control (-0.23, 95%CI:-0.43 to -0.03; P=0.026), but not for the comparison between PRT and control (-0.13, 95%CI:-0.37 to 0.12; P=0.307) or combination therapy and control (-0.11, 95%CI:-0.36 to 0.13 P=0.374). Conclusion: When compared with a control intervention, AEx therapy is effective for lowering VAT. Conversely, when compared with control, PRT in isolation or in combination with AEx may not reduce VAT. These data suggest that AEx is more efficacious for reducing VAT in overweight/obese populations with type 2 diabetes. Due to the small sample size of multi-modal and resistance training interventions, further investigation is needed to determine the efficacy of these therapies for VAT benefit.