Background Weight loss achieved via energy restriction leads to significant losses in muscle and bone mass, potentially increasing risk for sarcopenia and osteoporosis. High-intensity resistance and impact training (HiRIT) might attenuate weight loss–induced musculoskeletal declines. Our objective was to compare changes in physical function and body composition in older adults with obesity undertaking dietary weight loss combined with HiRIT or aerobic training (AT).

Methods Sixty older adults (aged ≥ 60 years) with obesity (dual-energy x-ray absorptiometry determined body fat percentage ≥ 30% in men and ≥ 40% in women) and a mobility limitation (Short Physical Performance Battery [SPPB] score ≤ 11) were randomly assigned to either 12 weeks of supervised, centre-based HiRIT or self-directed, home-based AT while consuming a hypocaloric diet (750–1000 kcal/day reduction in energy intake). Changes in physical function (primary outcome: gait speed) and body composition were compared between groups.

Results A total of 49/60 randomised participants (mean age: 69.6 ± 6 years; 58% women; mean BMI: 32.9 ± 4.1 kg/m2) completed the trial. Gait speed increased following HiRIT compared with AT (mean difference: 0.07 m/s [95% CI: 0.01, 0.13]). Chair stand times decreased in both groups (HiRIT: −1.3 s [95% CI: −2.1, −0.4] vs. AT: −0.8 s [95% CI: −1.6, −0.04]) and HiRIT, but not AT, increased handgrip strength (HiRIT: 2.2 kg [95% CI: 0.6, 3.9] vs. AT: 0.7 kg [95% CI: −0.9, 2.3]) and SPPB scores (HiRIT: 0.9 [95% CI: 0.4, 1.3] vs. AT: 0.4 [95% CI: −0.04, 0.8]). Similar decreases in total body mass (HiRIT: −5.1 kg [95% CI: −6.7, −3.4] vs. AT: −4.9 kg [95% CI: −6.5, −3.3]), fat mass (HiRIT: −3.6 kg [95% CI: −5.0, −2.2] vs. AT: −3.3 kg [95% CI: −4.7, −2.0]), visceral fat (HiRIT: −32.1 cm2 [95% CI: −47.4, −16.8] vs. AT: −31.4 cm2 [95% CI: −46.1, −16.8]) and appendicular lean mass (HiRIT: −0.8 kg [95% CI: −1.4, −0.2] vs. AT: −1.2 kg [95% CI: −1.8, −0.6]) were observed. HiRIT was well tolerated with only seven minor adverse events compared with five reported in those who completed AT.

Conclusion HiRIT appears to be safe and more effective than AT for improving gait speed in older adults with obesity undertaking dietary weight loss. Additional trials with larger sample sizes and longer durations are warranted to explore whether HiRIT can attenuate weight loss–related muscle and bone mass declines. Trial Registration: Australian New Zealand Clinical Trials: ACTRN12618001146280.