Substrate oxidation differences between high- and low-intensity exercise are compensated over 24 hours in obese men

Abstract

OBJECTIVE: Exercise has been proposed as a tool for the prevention of obesity. Apart from an effect on energy expenditure, in particular low-intensity (LI) exercise might also influence substrate metabolism in favour of fat oxidation. It is however unclear what is the most beneficial exercise regime for obese people. We therefore studied the effect of either high-intensity (HI) or LI exercise on 24 h energy expenditure (24 h EE) and substrate metabolism. METHODS: Eight healthy obese male volunteers (age: 3871 y, BMI: 3171 kg/m 2 , W max : 235716 W) stayed in the respiration chamber for two nights and the day in-between. In the chamber they cycled either at a HI (three times 30 min in a interval protocol (2.5 min 80/50% W max )) or LI (three times 60 min continuously at 38% W max ) protocol with an equicaloric energy expenditure. In the chamber subjects were fed in energy balance (37/48/15% of energy as fat/carbohydrate/protein). RESULTS: The 24 h EE was not significantly different between protocols. In both protocols, sleeping metabolic rate (SMR) was elevated after the exercise (average þ 6.7%). The 24 h respiratory quotient (24 h RQ) was not different between protocols. During exercise, RQ was higher in the HI compared to the LI protocol (0.93 vs 0.91 resp., Po0.05), whereas in the postexercise period RQ tended to be lower in the HI compared to the LI protocol (P ¼ 0.06). CONCLUSION: 24 h EE is not differently affected by HI or LI exercise in obese men. Similarly, the differences in HI and LI exercise, RQ are compensated postexercise leading to similar substrate oxidation patterns over 24 h independently of the level of exercise intensity.

Concept of fat balance in human obesity revisited with particular reference to de novo lipogenesis

“…In typical nutritional studies, fat balance is evaluated over 24 h (or more) using a respiration chamber to continuously measure energy expenditure and substrate oxidation. [1][2][3][4] Fat balance is closely linked to energy balance when considered over weeks and months. This means that continuous positive energy balance is essential to gain fat.…”

Exercise, substrate oxidation and energy balance

“…[8][9][10][11] Our purpose is not to negate the therapeutic interest of HI exercise, but to further develop the medical use of LI training by proposing a targeting procedure based on exercise calorimetry. 6 In this respect, we could notice that in Saris's paper, 3 the LI exercise was targeted at 38% of W max , based on studies in healthy controls, while in our personal works the level at which lipid oxidation reaches a maximum appears to be shifted to lower intensities, around 30%, with a wide interindividual variability. Thus, in our paper, the fat burning exercise session is set at 29% of W max .…”

“…2 High-intensity exercise depletes muscular glycogen stores and leads to higher postexercise fat oxidation. 3,4 Conversely, low-intensity exercise with high-fat oxidation is followed by increased postexercise carbohydrate oxidation, compared with a highintensity exercise condition. This means that high-fat oxidation during exercise is followed by low postexercise fat oxidation and vice versa.…”

Response to Fogelholm

“…6 In this respect, we could notice that in Saris's paper, 3 the LI exercise was targeted at 38% of W max , based on studies in healthy controls, while in our personal works the level at which lipid oxidation reaches a maximum appears to be shifted to lower intensities, around 30%, with a wide interindividual variability. Thus, in our paper, the fat burning exercise session is set at 29% of W max .…”

“…3,4 Conversely, low-intensity exercise with high-fat oxidation is followed by increased postexercise carbohydrate oxidation, compared with a highintensity exercise condition. This means that high-fat oxidation during exercise is followed by low postexercise fat oxidation and vice versa.…”