Efficacy of low-impact interval training at reducing epicardial adipose tissue (EAT) volume in adults with abdominal obesity: A randomized controlled trial

Excess adiposity or obesity is a major but modifiable risk factor for cardiovascular diseases (CVD), which are the leading cause of death globally and pose a substantial economic burden on the healthcare system worldwide. Not all fat depots in humans contribute equally to CVD. Epicardial fat, also known as epicardial adipose tissue (EAT), is the only fat depot in humans that has no anatomical barrier separating it from its target organ – the myocardium (i.e., they share the same microcirculation). The volume of EAT is an independent risk factor for CVD in individuals with obesity; a 1-SD increase in the volume of EAT is associated with a 37% increased risk of heart failure. An unhealthy lifestyle and aging result in the accumulation of EAT. Several clinical trials have attempted to modulate EAT volume using pharmacological interventions; however, this approach is expensive and comes with unpleasant side effects. Nonpharmacological interventions, such as endurance exercise, are effective in reducing the EAT volume, but fear of commitment to endurance exercise, physical limitations, and psychological barriers often prevent people with abdominal obesity from performing endurance exercise. Low-impact interval training (LIIT) could be an alternative way to safely, efficiently, and effectively reduce EAT in adults with abdominal obesity. Indeed, our pilot study showed that once-a-week LIIT (once-LIIT) safely and significantly reduced EAT and visceral fat and increased skeletal muscle mass. This proposed study aims to examine the efficacy of the once-LIIT in reducing EAT volume and improving health-related fitness in a clinical trial setting. Adults with abdominal obesity will be recruited and randomly assigned to intervention groups or exercise counseling control group (EC_con). EAT, abdominal adipose tissue, and gluteal-femoral adipose tissue will be assessed by magnetic resonance imaging (MRI). Health-related fitness, cardiometabolic disease risk factors, blood chemistry, psychological measures, physical activity level, and diet habits will also be carefully assessed. All measurements will be conducted at baseline (month 0), completion of the intervention (week 16), and follow-up (week 52). This study will provide high-quality clinical evidence of the efficacy of onceLIIT at reducing EAT volume in humans. Besides bridging the existing research gap between once-LIIT, EAT, and body composition, this novel exercise modality will also provide individuals with abdominal obesity an opportunity to lower their risk of developing CVD in an efficient and cost-effective manner. Given the convenience of once-weekly dosing, this intervention is expected to improve exercise adherence in inactive individuals with obesity.