Exercise intensity influences body composition: a 6-month comparison of high-intensity interval, moderate- and low-intensity training among healthy older adults

Abstract

Objective: To determine whether exercise of higher intensity can elicit greater improvements in body composition among older adults, given that body composition is implicated in the progression of chronic disease. Study design: Sub-study of a randomised controlled trial (ACTRN12618000700235). Main outcome measures: Healthy older adults (n = 123, average age 72.0 years, body mass index 25.8 kg/m2) completed three 45-min supervised exercise sessions per week for 6 months. Participants were randomised to treadmill-based moderate-intensity training (n = 45), or high-intensity interval training (n = 41) or a low-intensity active control condition (n = 37), with individualised heart-rate prescription. Dual-energy x-ray absorptiometry was used to quantify body composition at baseline, and at 3 and 6 months. Results: For fat mass, both high- (p = 0.001) and moderate-intensity groups (p = 0.016) demonstrated similar reductions that were both larger than control, post-intervention. Only moderate-intensity training was associated with reductions in fat-free mass (FFM) at 0–3 (p = 0.005) and 0–6 months (p = 0.050), potentially exacerbating age-related reductions in muscle and other lean tissues. Overall, high-intensity training had greater between-group raw difference in lean mass than moderate-intensity training at 6 months (p = 0.042) and this group was the only one with a net improvement in body fat percentage (p = 0.017). Moderate-intensity (p = 0.009) and high-intensity training (p = 0.023) demonstrated comparable improvements in visceral adipose tissue over 0–6 months. Conclusions: High-intensity training reduced fat and maintained lean mass in apparently healthy older adults, though changes were small and not clinically meaningful compared with exercise of lower intensity and considering measurement error. Where appropriate and feasible, higher-intensity exercise training may be considered to support improvements in health-related body composition in older adults. Protocol registration: ACTRN12618000700235.