Department Endocrinology and Metabolism, University Medicine, Peninsula Medical School, Plymouth, UK.
Int J Obes (Lond). 2011 Oct;35(10):1270-6. doi: 10.1038/ijo.2011.163. Epub 2011 Aug 9.
Intuition tells us that physical activity is central to weight reduction in obese children. Evidence, on the other hand, suggests that increases in physical activity are difficult to achieve in the short term, and may not be possible in the long term. One explanation could be an 'activitystat', a feedback loop in the child's brain that controls physical activity according to a set point. This brief article, which argues that it may not be possible to modulate the activity of children, reviews the principles of feedback control as they apply to physical activity, discusses evidence for its central control, and demonstrates how a physical activity control loop might operate to defend the set point. Studies restricted to objective measurement suggest that the physical activity of children varies in a systematic, rather than random manner. It varies little from environment to environment, from year to year or from place to place. Where children undertake more activity at one time of day, they appear to compensate at another. Systematic variation of this kind implies control, and the control of physical activity appears to lie with the child, not with his environment. Perturbation (temporary change in response to disturbance) during short-term physical activity interventions may be mistaken for modulation (permanent change in set point), a fundamentally different response. Perturbation lasts no longer than the disturbance that causes it, and there is little evidence that interventions raise activity long term, if at all.
直觉告诉我们，体力活动对于肥胖儿童的体重减轻至关重要。另一方面，有证据表明，短期内增加体力活动很困难，长期内可能也无法实现。一种解释可能是“活动状态”，即控制孩子体力活动的大脑中的反馈回路，根据设定点进行控制。本文简要讨论了反馈控制原理在体力活动中的应用，探讨了其中心控制的证据，并展示了体力活动控制回路如何运作以维持设定点。研究仅限于客观测量，表明儿童的体力活动以系统而非随机的方式变化。它在不同环境、不同年份或不同地点之间变化不大。在一天中的某个时间进行更多活动的儿童，似乎会在另一个时间进行补偿。这种系统变化意味着控制，而体力活动的控制似乎在于孩子本身，而不在于其环境。短期体力活动干预期间的干扰（对干扰的暂时反应变化）可能会被误认为是调节（设定点的永久变化），这是一种根本不同的反应。干扰持续时间不会超过引起干扰的时间，而且几乎没有证据表明干预措施会长期提高活动水平，如果有的话。
