Kriketos A D, Sharp T A, Seagle H M, Peters J C, Hill J O
Center for Human Nutrition, University of Colorado Health Sciences Center, Denver 80262, USA.
Med Sci Sports Exerc. 2000 Apr;32(4):805-11. doi: 10.1097/00005768-200004000-00013.
This study investigated the contributions of physical fitness and body composition to 24-h fat oxidation in adults under sedentary conditions in a whole-room calorimeter.
The following measurements were studied in 109 adults (49 male/45 female) at least 36 h after a bout of exercise: 1) aerobic fitness level assessed by VO2max, 2) body composition determined by underwater weighing, 3) resting metabolic rate (RMR) after an overnight fast, and 4) 24-h energy expenditure (EE) and substrate oxidation determined in a whole-room calorimeter. While in the calorimeter, subjects were provided with a diet (15% protein, 30% fat, and 55% carbohydrate) estimated to produce energy balance on a sedentary day and of similar nutritional composition to their daily dietary intake.
We found strong negative correlations between VO2max and % body fat in both male and female subjects, but no relationship between VO2max and 24-h EE under the sedentary conditions of this study. In male subjects, VO2max (mL O2 x kg(-1) fat-free mass x min(-1)) was negatively related to fat oxidation (r = -0.397, P < 0.005), and fat oxidation was more closely related to fat mass (r = 0.434, P < 0.0002) than to fat-free mass (r = 0.165, NS). In contrast, none of these relationships were significant in females.
The results show that in male subjects under sedentary conditions, 24-h fat oxidation is positively related to body fat mass and negatively related to VO2max (the marker used here for level of physical fitness). This supports our hypothesis that regularly active males maintain lower body fat stores as the low contribution to daily fat oxidation from a lower body fat mass is counterbalanced by the high contribution to fat oxidation from daily physical activity. The lack of a relationship between VO2max and 24-h EE under the sedentary conditions of this study suggests that the major effects of physical activity on total daily EE and fat oxidation may occur during and relatively quickly after an exercise bout. Further, these data also suggest that cessation of regular exercise will likely be associated with a high risk of positive fat balance and weight gain.
本研究在全室热量计中，调查了久坐不动的成年人的体能和身体成分对24小时脂肪氧化的影响。
对109名成年人（49名男性/45名女性）在一次运动后至少36小时进行以下测量：1）通过最大摄氧量评估有氧适能水平，2）通过水下称重确定身体成分，3）禁食过夜后的静息代谢率（RMR），4）在全室热量计中测定24小时能量消耗（EE）和底物氧化。在热量计中时，为受试者提供一种饮食（15%蛋白质、30%脂肪和55%碳水化合物），估计该饮食在久坐日可产生能量平衡，且营养成分与他们的日常饮食摄入量相似。
我们发现，男性和女性受试者的最大摄氧量与体脂百分比之间均存在强负相关，但在本研究的久坐条件下，最大摄氧量与24小时EE之间无关联。在男性受试者中，最大摄氧量（毫升氧气×千克（-1）去脂体重×分钟（-1））与脂肪氧化呈负相关（r = -0.397，P < 0.005），且脂肪氧化与脂肪量的相关性（r = 0.434，P < 0.0002）比与去脂体重的相关性（r = 0.165，无显著性差异）更密切。相比之下，这些关系在女性中均不显著。
结果表明，在久坐条件下的男性受试者中，24小时脂肪氧化与体脂量呈正相关，与最大摄氧量（此处用作体能水平的指标）呈负相关。这支持了我们的假设，即经常运动的男性保持较低的体脂储存，因为较低的体脂量对每日脂肪氧化的低贡献被日常身体活动对脂肪氧化的高贡献所抵消。在本研究的久坐条件下，最大摄氧量与24小时EE之间缺乏关联，这表明身体活动对每日总EE和脂肪氧化的主要影响可能发生在运动期间和运动后相对较快的时间内。此外，这些数据还表明，停止定期运动可能会与脂肪正平衡和体重增加的高风险相关。
