Governments are always telling us to eat less and exercise more to be healthier, but this presents an obvious problem.

　　政府总是告诉我们要少吃多运动才能更健康，但这却有一个明显的问题。

　　Being active is liable to make you hungrier, so there's a risk you end up eating extra tocompensate, and putting on more weight than if you'd never got off the sofa in the first place.

　　运动容易让你更饿，以至于你可能会吃更多东西来补充(体力)，比你一开始就没有从沙发上起身要增重更多。

　　Dieticians dream of the day when they can design diets for people where they are more active but don't get hungry in the process.

　　营养师梦想着有一天，他们可以为人们设计饮食，使他们更积极地参与运动，却不会感到饥饿。

　　Unfortunately it's trickier than you might think: we're still searching for the mechanism that governs how the energy we expend translates into our level of appetite. And as we shall see, that's by no means the only thing that makes this area complicated.

　　不幸的是，这比你想象的要复杂得多：我们仍然在探求把我们消耗的能量转化成食欲的机制。正如我们将看到的一样，这绝不是使这个领域变得复杂的唯一原因。

　　In an ideal world, the human body would be wired to immediately detect changes in the amount of energy we use and then give us the appetite to eat the right amount to balance it out.

　　在理想的世界里，人类的身体会立即检测出我们消耗的能量的变化，然后让我们有胃口吃适量的食物来相抵。

　　Alas not: we all get hungry two or three times a day, sometimes more, regardless of what we are getting up to.

　　可惜的是：不管我们做什么，我们每天都会饿上两三次，有时候会更多。

　　Our bodies also release far stronger signals about our appetite when we haven't eaten enough than when we've eaten too much.

　　与我们吃得过多的时候相比，在我们吃得不够的时候，我们的身体会释放出更强烈的食欲信号。

　　This poor daily feedback relationship helps to explain why obese people still experience strong feelings of hunger – that and all the cheap calorie-dense food that is widely available, of course.

　　这种糟糕的日常反馈关系有助于解释为什么肥胖的人仍然有强烈的饥饿感，以及那些廉价的高热量食物为什么会随处可见。

　　What could lie behind this difference? One possibility is that physiological processes change in people who do more exercise – for instance, their gut hormones might be released in different concentrations when they eat, potentially with a bearing on how much food they need.

　　造成这种差异的原因是什么呢?一种可能是，运动多的人的生理过程会发生变化。例如，他们进食时释放的肠道激素浓度可能会不同，这可能与他们需要多少食物有关。

　　One longstanding question, dating back some 60 years, is where metabolism fits into the picture. Some important work published in 2013 by a team in Leeds found that overweight people were hungrier and consumed more calories than thinner people.

　　一个存在已久的问题是，新陈代谢在其中起到了什么作用，这一问题可追溯至大约60年前。利兹的一个研究团队在2013年发表的重要研究表明，太胖的人比消瘦的人更容易饿，摄入的热量也更多。