The Appetite Workout
多跑步，能果腹
Every January, many people start working out, hoping to lose weight. But as studies attest, exercise often produces little or no weight loss — and even weight gain — and resolutions are soon abandoned. But new science suggests that if you stick with the right kind of exercise, you may change how your body interacts with food. It’s more than a matter of burning calories; exercise also affects hormones.
每到春暖花开时，许多人就开始了以降低体重为目的的锻炼。但是研究表明，锻炼对减重的效果微乎其微，甚至会令体重增加——于是他们立刻就放弃了。然而，新的研究表明，如果你坚持进行正确的锻炼方式，你有能力改变身体与食物的相互作用。这不仅仅关乎燃烧卡路里，锻炼还能影响荷尔蒙。
A 2012 study from the University of Wyoming looked at a group of women who either ran or walked and, on alternate days, sat quietly for an hour. After the running, walking or sitting, researchers drew blood to test for the levels of certain hormones and then directed the women to a room with a buffet. Human appetite is complicated, driven by signals from the brain, gut, fat cells, glands, genes and psyche. But certain appetite-related hormones, in particular ghrelin, which stimulates hunger, are known to be instrumental in determining how much we consume.
2012年，在怀俄明大学(University of Wyoming)的一项研究中，一组女性隔天跑步或步行一小时，另一天则静坐一小时。在她们跑步、步行或静坐后，研究人员抽血检查特定荷尔蒙的浓度，然后让她们进入自助餐房间。人的食欲很复杂，由大脑、肠道、脂肪细胞、腺体、基因和心理各个因素发出信号驱动。但是已知特定的食欲相关荷尔蒙，尤其是刺激食欲的胃促生长素，决定了我们吃进多少热量。
Studies have shown that exercise typically increases the production of ghrelin. Workouts make you hungry. In the Wyoming study, when the women ran, their ghrelin levels spiked, which should have meant they would attack the buffet with gusto. But they didn’t. In fact, after running they consumed several hundred fewer calories than they burned.
研究表明，锻炼通常会增加胃促生长素的分泌。运动令你更饥饿。在怀俄明大学的研究中，跑步的女性胃促生长素水平飙升，这意味着她们将在自助餐中大快朵颐。但并非如此。事实上，跑步之后，她们吃掉的卡路里比跑步消耗的还少几百。
Their restraint, the researchers said, was due to a concomitant increase in other hormones that initiate satiety. These hormones, only recently discovered and still not well understood, tell the body that it has taken in enough fuel; it can stop eating. The augmented levels of the satiety hormones, the authors write, “muted” the message from ghrelin. Sitting and, notably, walking did not change the blood levels of the women’s satiety hormones, and the walkers overate, consuming more calories at the buffet than they had burned.
研究人员认为，她们的克制是因为其他荷尔蒙的升高引发了饱腹感。科学界是在近期刚刚发现了这些荷尔蒙，还未对此获得充分了解，现在已知它能告诉我们的身体已经获得了足够的燃料，别再吃了。作者认为，这些“饱腹激素”的水平升高，“平息”了胃促生长素发出的信息。值得注意的是，静坐和步行均不能改变女性血液中饱腹激素的水平，步行的人甚至会吃得过多，在自助餐中吃下去的卡路里超过了她们运动消耗的量。
A related study published in December looked at the effects of moderate exercise, the equivalent of brisk jogging. It found that after 12 weeks, formerly sedentary, overweight men and women began recognizing, without consciously knowing it, that they should not overeat.
去年12月发表的一项相关研究探索了相当于慢跑的适度锻炼的作用。研究发现，12周后，原先久坐超重的人们开始感觉到他们不能吃得太多，尽管他们对此并不自知。
But not all exercise. Running, it would seem, better hones the body’s satiety mechanisms than walking. And longevity counts. You need to stick with the program for several months, Martins says, to truly fine-tune appetite control.
但是，并非所有的运动都这样。目前看来，跑步对调节人体饱腹机制的效果比步行好。饱腹机制与运动持续的时间也有关。马丁斯说，你需要坚持几个月，才能真正获得良好的食欲控制能力。
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