BACKGROUND: Obesity compounds aging-related declines in cardiorespiratory fitness, with accompanying fatigue and disability. This study determined the effects of two different levels of caloric restriction (CR) during aerobic training on cardiorespiratory fitness, fatigue, physical function, and cardiometabolic risk. METHODS: The INFINITE study was a 20-week randomized trial in 180 older (65 to 79 years) men and women with obesity (body mass index 30 to 45 kg/m2). Participants were randomly assigned to (i) aerobic training (EX; treadmill 4 days/wk for 30 minutes at 65% to 70% of heart rate reserve), (ii) EX with moderate (-250 kcal/d) CR (EX+Mod-CR), or (iii) EX with more intensive (-600 kcal/d) CR (EX+High-CR). Cardiorespiratory fitness (peak aerobic capacity, VO2peak, primary outcome) was determined during a graded exercise test. RESULTS: One hundred and fifty-five participants returned for 20-week data collection (87% retention). VO2peak increased by 7.7% with EX, by 13.8% with EX+Mod-CR, and by 16.0% with EX+High-CR, and there was a significant treatment effect (EX+High-CR 21.5 mL/kg/min, 95% confidence interval 19.8 to 23.2; EX+Mod-CR 21.2 mL/kg/min, 95% confidence interval 19.4 to 23.0; EX 20.1 mL/kg/min, 95% confidence interval 18.4 to 21.9). Both CR groups exhibited significantly greater improvement in self-reported fatigue and disability and in glucose control, compared with EX. CONCLUSION: Combining aerobic exercise with even moderate CR is more efficacious for improving cardiorespiratory fitness, fatigue and disability, and glucose control than exercise alone and is as effective as higher-dose CR.
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