Caloric restriction benefits on cardiorespiratory fitness and muscle strength with and without exercise training in humans: a systematic review and meta-analysis

Aim: To identify the true Caloric restriction (CR) effects on relative and absolute maximum oxygen uptake (VO2max) and muscular strength. Methods: A systematic review was conducted in 5 databases, up to November 2019. Twenty-eight controlled trials were included in the meta-analyses comparing CR alone vs. standard diet (CR vs. control) or comparing CR plus exercise training vs. exercise training alone (CR+EX vs. EX) on VO2max and muscle strength. Results: CR+EX had a positive effect on relative VO2max (1.13 [0.49; 1.78]ml/kg/min, p<0.001), but had no additional effect on relative muscle strength (0.41 [-0.28; 1.09], p=0.25) when compared to EX. CR significantly increased relative VO2max (2.08 [0.90; 3.27]ml/kg/min, p<0.001) and relative strength (0.47 [0.35; 0.59)], p<0.001), compared with standard diet. Complementary analysis confirmed significant reductions in total body mass, fat mass and muscle mass among all subgroups, as expected. Absolute VO2max and strength were not improved by CR+EX or CR when compared to EX and control, respectively. Conclusion: CR alone significantly improve relative VO2max and muscle strength in non-physically active individuals.