High-intensity interval training with energy restriction preserves lean tissue and improves glucose tolerance in obesity

Calorie restriction (CR) reduces body weight (BW) and adiposity, but is often less than expected due to hypometabolism produced by reductions in lean body mass (LBM). A comparable energy deficit created by combining CR and exercise energy expenditure (EE) has been shown to attenuate the reduction in EE produced by CR. Continuous moderate-intensity training (MIT) is commonly used to sustain energy balance or expedite weight loss, but high-intensity interval training (HIIT) may produce greater results. The purpose of this investigation was to determine if HIIT preserves LBM and improves energy metabolism to a greater extent than MIT in the presence of CR. Thirty-two 5-wk old male C57BL/6J mice were placed on a 45% kcal high-fat diet (HFD) for 11 weeks ( ad libitum). Mice were then randomized to 4 groups for 15 weeks: 1) HFD (n = 8; remain on HFD); 2) HFD with 25% CR (n = 8); 3) HFD with 25% energy deficit induced by 12.5% CR and 12.5% EE mediated through HIIT (n = 8); and 4) HFD with 12.5% energy deficit induced by 12.5% CR and 12.5% EE mediated through MIT. HIIT consisted of 9-12 intervals of 2.5-minutes of treadmill running at 0.18-0.30 m/s with 1 minute of passive recovery. MIT consisted of 35-50 minutes of continuous treadmill running at 0.13-0.21 m/s. Body composition was assessed by Quantitative Magnetic Resonance (QMR) and resting energy expenditure (REE) by indirect calorimetry. Glucose tolerance tests were performed on all groups at 1.0 g·kg-1 BW (i.p.), while insulin tolerance tests were performed at 0.75 mU·g-1 BW (i.p.). HFD produced a 92.3% increase in BW. REE was 15.6% lower in the CR group compared to Control (33.6 +/- 1.2 kJ/day to 39.8 +/- 1.4 kJ/day, p < 0.05). Twenty-five percent CR produced reductions in LBM and REE, whereas HIIT, but not MIT, preserved LBM and rescued CR-mediated reductions in REE, which was associated with improvements in glucose tolerance and insulin sensitivity. These results suggest that HIIT may produce a hypermetabolic state in the presence of CR, which could lead to long-term success in weight loss interventions.