A SIMPLE calculation lies at the heart of a lot of mainstream weight loss advice. If calories out exceed calories in, you will lose weight. It is why both exercise and diet are said to be key to staying trim, and why many of us feel we can make amends for overindulging by joining the gym or dusting off our running shoes.
简单的热量计算是许多主流减肥建议的核心。如果消耗的热量超过摄入的热量，就能减肥。这就是为什么运动和饮食都被认为是保持苗条身材的关键，也是为什么我们中的许多人认为可以通过加入健身房或重拾跑鞋上的灰尘来弥补过度放纵的过错。
But if you have ever increased how much exercise you do and found it did little to shed the pounds, you have probably had an inkling that the sums don’t add up. Despite tipping the balance in favour of calories out, the scales don’t budge. This is the so-called exercise paradox. Until recently, it has been explained away by the logic that exercise leaves people hungry so they eat more.
但是，如果你曾经增加了运动量，却发现它对减肥没有什么作用，你可能已经有了一个暗示，那就是总数加起来不多。尽管天平倾向于卡路里的消耗，但天平并没有改变。这就是所谓的运动悖论。直到最近，人们还用这样的逻辑来解释：锻炼会让人感到饿，所以他们会吃得更多。
It now turns out something weirder is going on. Working out a lot doesn’t appear to burn more calories than doing a little. In fact, going mad in the gym doesn’t seem to burn any more calories than moderate activity a few days a week and taking the stairs, for instance.
现在看来，发生了一些更奇怪的事情。大量锻炼并不比少量锻炼消耗更多的卡路里。事实上，在健身房发疯似乎并不比每周适度运动几天，比如爬楼梯燃烧更多的卡路里。
Researchers are scratching their heads as to how to reconcile this. And while it might be bad news for those who had hoped to run off those festive dinners, there is a flip side. Those who exercise intensively through a sense of guilt or obligation might be happier, and possibly wealthier, taking it easier.
研究人员正在为如何调和这一点而挠头。虽然这对那些希望跳过节日晚餐的人来说可能是个坏消息，但也有另一面。那些出于内疚感或责任感而进行高强度锻炼的人可能会更快乐，也可能更富有，更轻松。
Some of the biggest clues that something was up with the exercise and weight loss equation lie far from the gym, on the plains of Tanzania. Here, the Hadza people live as we all once did, as hunter-gatherers. The men walk about 10 kilometres each day, stalking game with bows and arrows, while women spend hours on the move, digging for wild tubers and picking berries.
一些明显的线索表明，运动和减肥方程式之间的关系远非健身房，而是在坦桑尼亚的平原上。在这里，哈扎人像我们一样，以狩猎采集为生。男人们每天步行约10公里，带着弓箭跟踪猎物，而女人们则要花上几个小时在路上，挖掘野生块茎和采摘浆果。
A few years ago, Herman Pontzer headed to Tanzania to study the Hadza and their metabolism. He wasn’t expecting to reveal any big mysteries around exercise. “It started off that we wanted to just ask a basic question: ‘How many calories do you need to burn to live as a hunter-gatherer?'” he says.
几年前，赫尔曼·庞泽前往坦桑尼亚研究哈扎人及其新陈代谢。他并没有期望揭示任何关于运动的大秘密。“一开始，我们只是想问一个基本的问题：‘作为一个狩猎采集者，你需要燃烧多少卡路里？’”他说。
To find out, Pontzer, an evolutionary anthropologist at Hunter College in New York, and his colleagues turned to the gold standard test for measuring daily energy expenditure, known as the doubly labelled water method. This involved the Hadza drinking water laced with slightly different forms of oxygen and hydrogen, called isotopes. How much of these isotopes are left in their urine accurately reveals how much energy they have used.
为了找到答案，纽约亨特学院的进化人类学家庞泽，和他的同事们采用了测量日常能量消耗的金标准测试，即双标水法。这涉及到哈扎饮用水中含有略微不同形式的氧和氢，称为同位素。有多少同位素留在他们的尿液中，可以准确地揭示了他们消耗了多少能量。
Far from burning through huge amounts of calories on their daily expeditions, the Hadza got through only slightly more than Westerners who drive to a job to sit all day, with the men using up about 2600 calories and the women 1900. “I couldn’t believe it,” says Pontzer.
哈扎人并没有在每天的探险中消耗大量的卡路里，他们只比开车上班、整天坐着的西方人多一点，男人消耗了大约2600卡路里，女人消耗了1900卡路里。“我简直不敢相信，”庞泽说。
The findings caused a stir. They called into question the widely accepted idea that sedentary lifestyles in many societies are responsible for the obesity epidemic. Instead, Pontzer and his team began to wonder whether our daily energy expenditure could have evolved to be fixed at these levels, regardless of whether we sit at a desk all day or search the plains looking for our next meal.
这一发现引起了轰动。一个被广泛接受的观点受到质疑——即久坐不动的生活方式是导致肥胖流行的主因。相反，庞泽和他的团队开始怀疑，我们的日常能量消耗是否可以进化到固定水平，无论我们是整天坐在办公桌前，还是在平原上寻找我们的下一顿饭。