Heymsfield Steven B, Gallagher Dympna, Kotler Donald P, Wang Zimian, Allison David B, Heshka Stanley
New York Obesity Research Center, St. Luke's-Roosevelt Hospital, New York, NY 10025, USA.
Am J Physiol Endocrinol Metab. 2002 Jan;282(1):E132-8. doi: 10.1152/ajpendo.2002.282.1.E132.
An enduring enigma is why the ratio of resting energy expenditure (REE) to metabolically active tissue mass, expressed as the REE/fat-free mass (FFM) ratio, is greater in magnitude in subjects with a small FFM than it is in subjects with a large FFM. This study tested the hypothesis that a higher REE/FFM ratio in subjects with a small body mass and FFM can be explained by a larger proportion of FFM as high-metabolic-rate tissues compared with that observed in heavier subjects. REE was measured by indirect calorimetry, FFM by dual-energy X-ray absorptiometry (DEXA), and tissue/organ contributions to FFM by whole body magnetic resonance imaging (MRI) in healthy adults. Four tissue heat-producing contributions to FFM were evaluated, low-metabolic-rate fat-free adipose tissue (18.8 kJ/kg), skeletal muscle (54.4 kJ/kg), and bone (9.6 kJ/kg); and high-metabolic-rate residual mass (225.9 kJ/kg). Initial evaluations in 130 men and 159 women provided strong support for two key, developed models, one linking DEXA FFM with MRI FFM estimates and the other linking REE predicted from the four MRI-derived components with measured REE. There was an inverse association observed between measured REE/FFM and FFM (r(2) = 0.17, P < 0.001). Allometric models revealed a similar pattern of tissue change relative to body mass across males and females with greater proportional increases in fat-free adipose tissue and skeletal muscle than in FFM and a smaller proportional increase in residual mass than in FFM. When examined as a function of FFM, positive slopes were observed for skeletal muscle/FFM and pooled low-metabolic-rate components, and a negative slope for residual mass. Our linked REE-body composition models and associations strongly support the hypothesis that FFM varies systematically in the proportion of thermogenic components as a function of body mass and FFM. These observations have important implications for the interpretation of between-individual differences in REE expressed relative to metabolically active tissue mass.
一个长期存在的谜题是，静息能量消耗（REE）与代谢活跃组织质量的比值，即REE/去脂体重（FFM）比值，在FFM较小的受试者中为何比FFM较大的受试者更大。本研究检验了这样一个假设：与体重较重的受试者相比，体重和FFM较小的受试者中较高的REE/FFM比值可以通过FFM中高代谢率组织所占比例更大来解释。在健康成年人中，通过间接测热法测量REE，通过双能X线吸收法（DEXA）测量FFM，通过全身磁共振成像（MRI）测量组织/器官对FFM的贡献。评估了对FFM有产热作用的四种组织，即低代谢率的无脂脂肪组织（18.8千焦/千克）、骨骼肌（54.4千焦/千克）和骨骼（9.6千焦/千克）；以及高代谢率残余质量（225.9千焦/千克）。对130名男性和159名女性的初步评估为两个关键的、已建立的模型提供了有力支持，一个模型将DEXA FFM与MRI FFM估计值联系起来，另一个模型将由MRI得出的四个成分预测的REE与测量的REE联系起来。观察到测量的REE/FFM与FFM之间呈负相关（r² = 0.17，P < 0.001）。异速生长模型显示，男性和女性相对于体重的组织变化模式相似，无脂脂肪组织和骨骼肌的比例增加幅度大于FFM，残余质量的比例增加幅度小于FFM。当作为FFM的函数进行检查时，观察到骨骼肌/FFM和合并的低代谢率成分呈正斜率，而残余质量呈负斜率。我们的REE-身体成分关联模型有力地支持了这样一个假设，即FFM中产热成分的比例会随着体重和FFM的变化而系统地变化。这些观察结果对于解释相对于代谢活跃组织质量而言REE的个体间差异具有重要意义。
