Ekelund U, Särnblad S, Brage S, Ryberg J, Wareham N J, Aman J
Medical Research Council Epidemiology Unit, Cambridge, UK.
Int J Obes (Lond). 2007 Jan;31(1):65-71. doi: 10.1038/sj.ijo.0803361. Epub 2006 May 2.
Differences in energy metabolism and physical activity (PA) may contribute to the long-term regulation of body weight (BW).
To examine the associations between metabolic determinants, energy expenditure and objectively measured components of PA with change in BW and fat mass (FM).
Prospective (4 years.), case-control study in obese (n=13) and normal weight (n=15) young adults.
At baseline, we measured resting metabolic rate, substrate oxidation, movement economy (ml O(2) kg(-1) min(-1)), aerobic fitness (VO(2max)), total and PA energy expenditure by doubly labelled water, and PA by accelerometry. Fat mass was measured by DXA. At follow-up we repeated our measurements of PA and FM.
Fat mass increased significantly (P<0.001) in both groups. Physical activity did not change between baseline and 'follow up'. Change in overall PA (counts per minute) was inversely associated with change in BW and (beta=-0.0124, P=0.054) and FM (beta=-0.008, P=0.04). Post hoc analyses suggested that this association was explained by changes in the normal weight group only (beta=-0.01; P=0.008; and beta=-0.0097; P=0.009, for BW and FM, respectively). Metabolic determinants, energy expenditure estimates and subcomponents of PA (i.e. time spent at different intensity levels) were not significantly associated with change in BW or FM.
Our results suggest an independent association between PA and FM. However, this association may differ depending on obesity status. The gain in FM, without any change in PA, may suggest that dietary intake is the major contributor to the positive energy balance.
能量代谢和身体活动（PA）的差异可能有助于长期调节体重（BW）。
研究代谢决定因素、能量消耗以及PA的客观测量成分与BW和脂肪量（FM）变化之间的关联。
对肥胖（n = 13）和正常体重（n = 15）的年轻成年人进行前瞻性（4年）病例对照研究。
在基线时，我们测量了静息代谢率、底物氧化、运动经济性（毫升氧气·千克⁻¹·分钟⁻¹）、有氧适能（最大摄氧量）、用双标水测量的总能量消耗和PA能量消耗，以及用加速度计测量的PA。通过双能X线吸收法测量脂肪量。在随访时，我们重复测量PA和FM。
两组的脂肪量均显著增加（P < 0.001）。基线和随访之间身体活动没有变化。总体PA的变化（每分钟计数）与BW的变化呈负相关（β = -0.0124，P = 0.054），与FM的变化呈负相关（β = -0.008，P = 0.04）。事后分析表明，这种关联仅在正常体重组的变化中得到解释（BW和FM的β分别为 -0.01；P = 0.008；以及β = -0.0097；P = 0.009）。代谢决定因素、能量消耗估计值和PA的子成分（即在不同强度水平下花费的时间）与BW或FM的变化没有显著关联。
我们的结果表明PA与FM之间存在独立关联。然而，这种关联可能因肥胖状态而异。FM增加而PA没有任何变化，这可能表明饮食摄入是正能量平衡的主要因素。
