Some of the weight loss articles out there these days are getting a little nutty. New scientific studies that shed light on how metabolism works are wonderful and valuable in their own right, but when findings get morphed into magical new “tips” for losing weight, something’s amiss. Some recent pieces in prestigious journals, which have sought to dispel the myths of weight loss and of the individual diets themselves, suggest that the medical community is also getting tired of the hype and the unfounded assumptions that permeate the public discussion.
如今，有些减肥文章实在有点离谱。关于新陈代谢系统如何运作的科学新研究本身是非常了不起且有价值的，但当研究结果被转化成新的减肥“秘笈”时，就会出现偏差。在权威杂志上，最近有些试图驱散减肥和个人饮食迷雾的文章表明，医学界也厌倦了公众讨论中那些天花乱坠的说法和毫无事实根据的假设。
When it comes down to it, the things we know to be true about weight loss are relatively simple, and certainly few. They’re also extremely effective when actually carried out. So, from the researchers who have studied this stuff for decades, here’s pretty much everything we know about weight loss today, whittled down to six points about how the body actually gains, loses, and maintains its weight.
归根结底，我们知道的行之有效的减肥方法相对而言比较简单，当然也很少，但真正做起来效果极好。所以，根据那些研究减肥几十年的研究人员所言，以下列出了到目前为止我们对减肥的几乎所有认识，归纳成有关体重如何增加、减少和保持的六项要点。
1. Dieting trumps exercising
1. 饮食胜过锻炼
We hear a lot that a little exercise is the key to weight loss – that taking the stairs instead of the elevator will make a difference, for instance. But in fact it’s much more efficient to cut calories, says Samuel Klein, MD at Washington University’s School of Medicine. “Decreasing food intake is much more effective than increasing physical activity to achieve weight loss. If you want to achieve a 300 kcal energy deficit you can run in the park for 3 miles or not eat 2 ounces of potato chips.” It’s as simple as that. Some studies have borne out this dichotomy, pitting exercise against diet and finding that participants tend to lose more weight by dieting alone than by exercise alone. Of course, both together would be even better.
我们经常听说锻炼是减肥的关键，例如爬楼梯而不是坐电梯将有助于减肥。但华盛顿大学医学院的医学博士萨缪尔•克莱恩（Samuel Klein）说，实际上减少卡路里摄入的效果要好得多。“节食是比锻炼更加有效的减肥方法。如果想消耗掉300卡路里，你需要在公园里跑3英里，或者少吃2盎司的土豆片。”就是这么简单。有些研究已经证实了这种巨大差别。这些研究将锻炼和饮食进行比较，发现只采用饮食方法的参与者往往会比只采用锻炼方法的参与者减少更多体重。当然，二者结合效果更好。
The problem is that when you rely on exercise alone, it often backfires, for a couple of reasons. This is partly because of exercise’s effects on the hunger and appetite hormones, which make you feel noticeably hungrier after exercise. “If you walk briskly for an hour and burn 400 kcal, ” says Klein, “and then have a beer and a slice of pizza afterwards because the exercise made you feel hungry…you will eat more calories than you have burned.” It may not always be beer and pizza, but people do tend to naturally compensate for the calories they expend.
问题在于，当你只依靠锻炼来减肥时，体重常常会反弹，这有几个原因，其中包括锻炼对饥饿感和食欲的作用，也就是你在锻炼后会感到更加饥饿。克莱恩说：“如果你快步走一个小时，消耗了400卡路里，然后由于锻炼使你感到饥饿而喝了瓶啤酒，吃了片披萨……那么你摄入的卡路里将超过你消耗的卡路里。”可能并不总是啤酒和披萨，但人们往往会自然而然地对消耗掉的卡路里进行补偿。
“This is an adaptive system, ” adds David Allison, PhD. “For every action there’s a reaction; that’s a law of physics, not of biology, but it seems that it also works in biological systems. This is why we often overestimate quite radically an effect of a particular treatment.” He points out that public health campaigns that, for example, urge people to take the stairs instead of the elevator or go on a nightly stroll – or, for that matter, even eat fewer calories – are unlikely to work, since they may fail to take into account the body’s compensatory mechanisms that can totally counteract the effect.
“这是自适应机制。”大卫•阿里森（David Allison）博士说，“每个作用力都有反作用力。这虽然是物理学而非生物学定律，但似乎也适用于生物系统。因此，我们常常会高估特定治疗方法的效果。”他指出，呼吁人们爬楼梯而不是坐电梯或者晚上出门散步的公共健康运动可能没有效果，因为它们没有考虑到补偿机制。
The other problem with exercise-without-dieting is that it’s simply tiring, and again, the body will compensate. “If the exercise made you tired so that you become more sedentary the rest of the day, you might not experience any net negative energy, ” says Klein. Some of the calories we burn come from our basic movements throughout the day – so if you’re wiped out after exercise, and more likely to sit on the couch afterwards, you’ve lost the energy deficit you gained from your jog.
锻炼而不节食的另外一个问题在于，锻炼使人疲倦，身体将再次进行补偿。“如果锻炼使你疲倦，那么在当天剩下的时间里你会变得更加不爱运动，结果你的卡路里可能不会有任何减少。”克莱恩说。在一天中，我们消耗的卡路里部分来自于我们的基本运动。因此，如果你在跑步锻炼后筋疲力竭，更有可能坐在沙发上不动，那么你就会失去你从锻炼中获得的那种能量消耗效果。
2. Exercise can help fix a “broken” metabolism, especially during maintenance
2. 锻炼有助于修复“失调的”新陈代谢，尤其是在保持体重期间
“People used to come into the doctor’s office and say, ‘My metabolism is broken!’” says James Hill, PhD, at the University of Colorado. “We never had any evidence that it actually was, until recently. We were wrong – it was!” While exercise may not be as important for weigh loss as calorie restriction, as Hill says, it’s important in another way: It begins to repair a broken metabolism.
“人们走进医生的诊室，常常会说，‘我的新陈代谢失调了！’”科罗拉多大学的詹姆斯•希尔（James Hill）博士说，“我们从未有过这方面的证据，直至最近。我们错了，新陈代谢真的会失调！”希尔指出，虽然锻炼的减肥效果比不上节食，但从另外一个方面来说，锻炼也很重要，因为它能修复失调的新陈代谢。
“A lot of what we know in this area comes from NASA, of the bed-rest studies, ” he says. “Within a couple of days of non-activity, the metabolism becomes inflexible. You start moving again, and it does start to change.” Your metabolism may not ever go back to “normal” (more on this below), but the evidence indicates that it can indeed pick up again, in large part through moving your body every day.
“我们在这个领域里的很多知识都来自于美国宇航局对卧床休息的研究。”他说，“如果一连几天都不运动，新陈代谢会变得萎靡不振。如果你再次开始运动，它就会振作起来。”你的新陈代谢可能永远回不到“正常水平”（下文将对此进行更多阐述），但有证据显示，它确实能再次振作，这在很大程度上是通过每天的身体运动实现的。
This is a large part of why exercise is critical in the maintenance phase, which is well known to be more difficult than the weight loss phase. Essentially, it buys us some wiggle room, says Michael Jensen, MD at the Mayo Clinic. “Exercise is very, very important for maintaining lost weight, and people who are not physically active are more likely to gain weight. We think it’s partly because in the extra calories burned from physical activity, you have a bit more flexibility in food intake, so you’re not so much relying on ridged changes in eating habits; it makes it more tolerable.”
这就是在保持体重阶段锻炼为什么至关重要的主要原因。众所周知，保持体重比减肥更加难以做到。梅奥诊所（Mayo Clinic）的医学博士迈克尔•詹森（Michael Jensen）说，从本质上讲，锻炼为我们留下了回旋余地。“锻炼对于保持减肥效果非常重要，不经常运动的人更有可能增加体重。我们认为，锻炼之所以非常重要，部分原因在于锻炼消耗了额外的卡路里，使你在食物摄入方面拥有更大的灵活性，这样你就不必大幅改变你的饮食习惯，这令人更加容易接受。”
3. You’re going to have to work harder than other people – possibly forever
3. 你将不得不比其他人更加努力地锻炼，可能永远如此
Though exercise can help correct a metabolism that’s been out of whack for a long time, the grisly reality is that it may not ever go back to what it was before gained weight. So if you’ve been overweight or obese and you lose weight, maintaining that loss means you’re probably going to have to work harder than other people, maybe for good. “The sad thing, ” says Hill, “is that once you’ve been obese or not moving for some time, it takes a little more exercise to maintain. It doesn’t come back to normal.” It’s not a pretty reality to face, but coming to grips with it is important, he says, so that you won’t get frustrated when you discover that you have to do more work over the long term than your friend who was never overweight.
虽然锻炼有助于修复长期絮乱的新陈代谢系统，但可怕的现实是，新陈代谢可能永远无法恢复到体重增加之前的状况。因此，如果你曾经超重或者肥胖，而你减了肥，那么保持这种减肥效果意味着你可能将不得不比其他人更加努力地锻炼，或许永远如此。希尔说：“悲哀的是，如果你曾经肥胖或者有段时间不曾运动，那么你需要进行更多的锻炼才能保持体重。新陈代谢系统不会恢复正常。”他说，这不是美好的现实，但勇于面对很重要。这样一来，当你发现自己不得不比你那些从未超重的朋友更加努力地长期锻炼时，你才不会感到沮丧。
Building muscle can help your body burn a few more calories throughout the day, but it’s also likely that you’ll have to work harder aerobically in the long run. “It’s not fair, but that’s the way it is, ” adds Hill. “Once you understand it, though, you know it and it’s better. Because you can work with it.”
锻炼能够帮助你的身体燃烧更多的卡路里，但你将不得不更加努力地长期进行有氧运动。“这不公平，但现实就是如此。”希尔说，“然而，当你弄懂后，你就会明白，情况就会好起来，因为你能够应付它。”
4. There’s no magical combination of foods
4. 没有完美的饮食搭配
We often think that if we can just discover the “right” combination of foods, we’ll magically lose weight or maintain what we’ve lost. There are low-fat diets, low-carb diets, low glycemic diets, Paleo diets, and a lot of iterations of all of these. Jensen points out that in fact there doesn’t seem to be any “right” diet, and there doesn’t seem to be any evidence that one particular diet will work better with an individual’s specific metabolism. “The big myth out there,” he says, “is that there’s a magical combination of foods – be it protein, vegetarian, and what have you – that’s going to be unique because of its unique interaction with your metabolism. We know pretty much that any diet will help you lose weight if you follow it. There’s no magic diet. The truth is that ALL Diets will work if you follow them.”
我们常常认为，如果我们能发现“正确的”饮食搭配，我们就可以如同魔法般的减肥或者保持减肥效果。现在已经出现了低脂饮食、低碳水化合物饮食、低胰岛素饮食、旧石器时代饮食（Paleo diets）以及所有这些饮食的很多种变体。詹森指出，实际上没有所谓的“正确”饮食，没有证据显示某种特定的饮食对新陈代谢系统更有好处。他说：“这里有个巨大的迷信，即有种魔法般的饮食搭配（蛋白质、素食和诸如此类）是独一无二的，因为它对新陈代谢会产生独一无二的作用。我们清楚地知道，如果你贯彻始终，任何饮食都能帮助你减肥。没有魔法般的饮食。实际上，如果你贯彻始终，所有饮食都能发挥作用。”
5. A calorie IS a calorie!
5.卡路里都是一样的！
And for energy balance, it’s the number of calories that matters. Weight loss on the Twinkie Diet proves this principle: Last year, Mark Haub at Kansas State University lost 27 pounds eating junk food. And this is pretty good proof of concept, says Yale University’s David Katz, MD, who has written extensively on the futility of the “is a calorie a calorie?” debate.
就能量平衡而言，卡路里的摄入量很重要。甜点饮食减肥法证明了这个原则。去年，堪萨斯州立大学的马克•豪布（Mark Haub）依靠垃圾食品使体重减少了27磅。耶鲁大学的医学博士大卫•卡特兹（David Katz）说，这是相当好的概念验证。卡特兹曾就“卡路里都是一样的吗？”的无用争论写了大量文章。
It’s certainly true – at least in theory and sometimes in practice – that all calories are created equal. “From the standpoint of body weight,” adds Marion Nestle, PhD, of NYU, “a calorie is a calorie no matter what it comes from. You can gain weight eating too much healthy food as well as unhealthy. From the standpoint of health, it’s better to eat your veggies…. It’s just a lot easier to overeat calories from junk food than healthy food. But it can be done.”
所有的卡路里都“生而平等”，这无疑是对的（至少在理论上和某些实际情况下是如此）。纽约大学的马里昂•奈斯特（Marion Nestle）博士说：“从体重的角度来讲，一单位卡路里就是一单位卡路里，无论它来自何处。吃太多的健康食品也会像不健康食品那样使体重增加。从健康的角度来讲，吃蔬菜更好……垃圾食品只是比健康食品更容易使人摄入过量的卡路里。但这个问题可以解决。”
But the source of calories obviously matters for other reasons. One, says Katz, is that “the quality of calories is a major determinant of the quantity we ingest under real world conditions.” First of all, no one overeats veggies, so on a practical level, that’s a non-issue. “But where the calories come from does matter in that they influence satiety,” he adds, and this is partly psychology and partly biology. In fact, the food industry has carved out a whole new area of food science to study the “bliss point,” in which foods are created to increase the amount it takes to feel satiated and full. On one hand, says Katz, “we have the ‘bliss point’ science to tell us that the food industry can process foods to increase the calories it takes to reach satisfaction. We have the reciprocal body of work, including the Harvard study of the ONQI, showing that ‘more nutritious’ means, among other things, the opportunity to fill up on fewer calories.”
但卡路里的来源明显很重要，这有几个原因。卡特兹说，一个原因是“卡路里的质量是我们在现实环境下，卡路里摄入量的主要决定因素”。首先，没人会吃过多的蔬菜，因此从实际层面上来讲，这不是个问题。“但卡路里的来源确实很重要，因为它会影响到人们的饱腹感。”他说。这涉及到心理学和生物学。实际上，食品行业已经开辟出了一个全新的食品科学领域来研究“幸福点”，也就是制造食品来增加产生饱腹感所需的卡路里。卡特兹说，一方面，“‘幸福点’科学告诉我们食品行业能够通过食品加工来增加产生饱腹感所需的卡路里。包括哈佛大学的整体营养质量指数（ONQI）研究在内的相关研究显示，‘更多营养’意味着摄入较少的卡路里就能吃饱的机会。”
It’s true that types of foods you eat may, over time, affect your metabolic profile, so they may also matter in this way, but when it boils down, sticking to any reduced-calorie diet will create the energy deficit needed to lose weight. So the point is not to question what a calorie is, but rather to understand that we need to “trade up” our foods, says Katz – exchange the very dense, calorie-packed foods for foods that are less calorie-dense and more nutritionally dense: these are the ones that are bulkier, less energetically rich, have more or higher quality protein, are lower on the glycemic index, and more fibrous.
你吃的食物种类会逐渐影响到你的新陈代谢。因此，从这个方面来说，食物种类也很重要。而当能量被燃烧掉时，坚持低卡路里的饮食会产生能量不足的情况，而这正是减肥所需要的。卡特兹说，关键不在于问卡路里是什么，而在于知道我们需要“升级”我们的食物，把富含卡路里的食品换成卡路里较低、而营养更高的食品，这些食品块头更大，热量较少，拥有更多或更高质量的蛋白质，含糖量更低，更富含纤维。
6. It’s all about the brain
6. 一切都关乎大脑
As my colleagues have reported (here and here), when it comes down to it, it’s not the body or the metabolism that are actually creating overweight or obesity – it’s the brain. We all know intuitively that poor decisions are what make you gain weight and better ones are what make you lose it. The problem is that over time, the poor decisions lead to significant changes in how the brain governs – and, amazingly, responds to – the hunger and satiation processes. Years of any kind of behavior pattern lay down neural tracks, and overeating is no exception.
正如我的同事们报道的那样，说到底，真正造成超重或肥胖的不是身体或新陈代谢，而是大脑。我们凭直觉认为，糟糕的决定使体重增加，更好的决定使体重减少。但问题在于，随着时间的推移，糟糕的决定会显著改变大脑控制（和应对）饥饿和饱腹感的方式。任何长期的行为模式都会在大脑里留下痕迹，暴饮暴食也不例外。
The good news is that there’s increasing evidence that the brain can, in large part, “fix” itself once new behavior patterns emerge (i.e., calorie restriction, healthy food choices, and exercise). While there may be some degree of “damage” to the brain, particularly in how hunger and satiety hormones function, it can correct itself to a large degree over time. The key is that the process does take time, and like any other behavior change, is ultimately a practice. “We want to change behavior here,” says Hill. “Anyone that tells you it’s going to happen in 12 weeks, that’s bogus. We’re trying to rewire the brain. Neurobiology has told us so much about what’s going on in weight gain and weight loss. It takes a long time to develop new habits, rituals, routines. This takes months and years. But it will happen.”
好消息是，越来越多的证据显示，当新的行为模式出现后（例如限制卡路里摄入量、选择健康食品和锻炼），大脑能够在很大程度上“修复”自己。虽然大脑会留下某种程度的“损伤”，尤其是在饥饿和饱腹激素如何发挥作用方面，但大脑很大程度上能够逐渐自我修复。关键之处在于，这个过程需要时间，而且就像其他的行为模式改变一样，最终需要付诸实践。希尔说：“假如我们想改变行为模式，有人对你说只需要12周时间就能办到，那他就是在说大话。我们试图改变大脑。神经生物学已经告诉了我们有关体重增加和减少的很多知识。形成新的习惯、模式和固定行为需要很长时间，可能是几个月，也可能是几年。但最终是能做到的。”
So boiling it down even further: reduce calories, eat better, exercise, and most of all, remember it is a practice that has to be repeated over time – months or years. The fact that you’ll have to work harder at maintenance than your never-overweight best friend is depressing, but it’s worth coming to terms with. And, most important to remember, your brain (the organ behind all this, after all) is plastic, and it will respond to the changes you make – better than you think. And so will your body.
所以进一步归纳如下：减少卡路里摄入量、吃得更健康、锻炼，最重要的是持之以恒，可能是数月或几年。与那些从未超重的朋友相比，你在保持体重方面将不得不更加努力，这虽然令人郁闷，但值得忍耐。最需要牢记的是，你的大脑（决定这一切的器官）是可塑的，它将回应你作出的改变，效果会比你以为的更好。你的身体也将作出回应。
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