The endless array of diets that claim to help you shed pounds tend to fall into two camps: low fat or low carbohydrate¹. Some companies even claim that genetics can tell us which diet is better for which people.

声称能帮助你减肥的饮食方式不计其数，它们往往分为两大阵营：低脂或低碳水化合物。一些公司甚至声称基因可以告诉我们哪种饮食更适合哪些人。

A rigorous recent study sought to settle the debate, and it had results to disappoint both camps. On the hopeful side, as The New York Times noted², people managed to lose weight no matter which of the two diets they followed.

最近，一项严谨的研究试图解决这场争论。研究得出的结果让两个阵营都失望了。乐观的一面是，正如《纽约时报》所指出的那样，两种饮食方式无论遵循哪一种都能减肥。

The study is worth a closer look to see what it did and did not prove.

这项研究值得我们去细究它证明了什么，没有证明什么。

Researchers at Stanford University took more than 600 people (which is huge for a nutrition study) aged 18 to 50 who had a body mass index of 28 to 40 (25-30 is overweight, and 30 and over is obese³). The study subjects had to be otherwise healthy. They couldn’t even be on statins, or drugs for Type 2 diabetes⁴ or hypertension, which might affect weight or energy expenditure⁵. They were all randomly⁶ assigned to a healthful low-fat or a healthful low-carbohydrate diet, and they were clearly not blinded to which group they were in.

斯坦福大学(Stanford University)的研究人员挑选了600多名（这个数字对营养学研究来说堪称巨大）年龄在18到50岁，身体质量指数在28到40之间（25到30之间为超重，30或以上为肥胖）的研究对象。他们在其他方面必须保持健康，甚至不能服用他汀类药物，也就是治疗2型糖尿病或高血压的药物。这些药物可能会影响体重或能量消耗。所有人被随机分到健康低脂饮食组或健康低碳水化合物饮食组，但他们显然不知道自己属于哪一个组。

All participants attended 22 instructional sessions over one year in groups of about 17 people. The sessions were held weekly at first and were then spaced out so that they were monthly in the last six months. Everyone was encouraged to reduce intake⁷ of the avoided nutrient⁸ to 20 grams per day over the first eight weeks, then participants slowly added fats or carbohydrates⁹ back to their diets until they reached the lowest level of intake they believed could be sustained for the long haul.

在一年时间里，所有参与者以大约17人一个小组的形式上了22次指导课。这些课程一开始每周一次，然后拉开间距，到最后六个月变成每月一次。在前八周，每个人都被鼓励将应避免的营养物质的摄入量降低到一天20克，然后参与者慢慢恢复各自饮食中的脂肪或碳水化合物摄入量，直到达到他们认为可以长期维持的最低摄入量。

Everyone was followed for a year (which is an eternity¹⁰ for a nutrition study). Everyone was encouraged to maximize vegetable intake; to minimize added sugar, refined flour and trans fat intake; and to focus on whole foods that were minimally¹¹ processed. The subjects were also encouraged to cook at home as much as possible.

每个实验对象都被追踪了一年（这对营养学研究来说这是很长一段时间）。所有人都被鼓励尽量多摄入蔬菜，少摄入添加糖、精制面粉和反式脂肪酸，并重点食用简单加工的全天然食物。实验对象还被鼓励尽可能在家做饭。

All the participants took a glucose¹² tolerance¹³ test as a measurement of insulin sensitivity. Some believe that insulin resistance or sensitivity may affect not only how people respond to diets, but also how well they adhere to them. The participants were also genotyped, because some believe that certain genes¹⁴ will make people more sensitive to carbohydrates or fat with respect to weight gain. About 40 percent of participants had a low-fat genotype, and 30 percent had a low-carbohydrate genotype.

所有参与者都接受了葡萄糖耐量测试，以衡量他们的胰岛素敏感性。一些人认为，胰岛素抵抗或敏感性不仅会影响人们对饮食方式的反应，还会影响他们对饮食方式的坚持情况。参与者还接受了基因分型，因为一些人认为，就体重增加而言，某些基因会使人们对碳水化合物或脂肪更敏感。大约40%的参与者属于低脂基因型，30%属于低碳水化合物基因型。

Data were gathered at the beginning of the study, at six months and at one year. At three unannounced times, researchers checked on patients to see how closely they were sticking to the instructions.

研究过程中收集了三次数据，分别是研究开始、六个月和一年时。研究人员分三次在不事先通知的情况下查看患者严格遵守指导的情况。

This was a phenomenally well-designed trial.

这是一项设计得极为出色的试验。

People did change their diets according to their group assignment. Those in the low-fat group consumed, on average, 29 percent of their calories from fats, versus¹⁵ 45 percent in the low-carbohydrate group. Those in the low-carbohydrate group consumed 30 percent of their calories from carbohydrates, versus 48 percent in the low-fat group.

人们的确会根据分组改变自己的饮食。低脂组的人消耗的热量平均29%来自脂肪，低碳水组的人45%的热量来自脂肪。低碳水组消耗的热量30%来自碳水化合物，低脂组48%的热量来自碳水化合物。

They did not, however, lose meaningfully different amounts of weight. At 12 months, the low-carbohydrate group had lost, on average, just over 13 pounds, compared with more than 11.5 pounds in the low-fat group. The difference was not statistically¹⁶ significant.

然而，他们的体重减少并没有什么实质性的不同。在12个月时，低碳水组平均只减了13磅多一点，对比低脂组减少了超过11.5磅。该差异没有统计学意义。

Insulin sensitivity didn’t make a difference. People who secreted¹⁷ more or less insulin lost no more or less weight in general on either a low-fat or low-carbohydrate diet. Genetics didn’t make a difference either. People who had genes that might indicate that they would do better on one diet or the other didn’t.

胰岛素敏感性并没有影响。人们分泌的胰岛素不论多少，在低脂或低碳水饮食中的减重差别都不大。基因也没什么差别。一些人有的基因可能意味着他们会在某类饮食中表现更好，而在另一种饮食中则没那么好。

In fact, when you look at how every single participant in this study fared on the diet to which he or she was assigned, it’s remarkable¹⁸ how both diets yielded an almost identical, curving range of responses — from lots of weight lost to a little gained. It wasn’t just the averages.

事实上，如果观察研究中每个单一参与者根据自己所分配到的饮食进食，人们会惊讶于两种进食都产生了几乎相同的曲线反应范围——从大幅减重的到轻微增重的。不仅仅是平均数。

Some have taken this study to prove that avoiding processed foods, eating more whole foods, and cooking at home leads to weight loss. While I’d like that to be true — I have advocated this healthful approach in my Upshot article on food recommendations and in a recent book — that’s not what this study showed. Although that advice was given to all participants, there was no control group in which that advice was omitted, and so no conclusions can be made as to the efficacy of these instructions.

一些人用这项研究证明，避开加工食品、吃更多天然食品并且在家下厨就能减肥。虽然我希望这是真的——在“结语”(Upshot)专栏有关食物的文章以及最近的一本书中，我都提倡过这种健康的方法——但本次研究并未表现出这一点。虽然所有参与者都得到了这一建议，但并没有未得到该项建议的对照组，因此，不能得出有关这些建议是否有效的结论。

Others have taken this study as evidence debunking¹⁹ the idea that counting calories is the key to weight loss. While that wasn’t the main thrust of this study, nor the instructions given, participants did reduce their intake by an average of 500-600 calories a day (even if they didn’t count them). This study didn’t prove the unimportance of calories.

有人用这项研究来驳斥卡路里是减肥关键的说法。虽然这不是研究的主要目的，给出的指示里也没有，但参与者每天确实减少了500到600卡路里的摄入量（即使他们没在计算）。这项研究不能证明卡路里不重要。

The researchers also asked everyone, not just those in the low-carb group, to avoid “added sugars.” Therefore, we can’t really say anything new about added sugars and weight loss.

研究人员还要求所有人避免“添加糖”，而不只是只对低碳水化合物组有这个要求。因此，对于添加糖和减肥的关系我们并没有什么新消息。

What this study does show is that people who have staked a claim on one diet’s superiority over another don’t have as strong a case as they think. It’s hard to overstate how similarly these two diets performed, even at an individual level.

这项研究能够表明的是，那些主张某种饮食比另一种饮食更好的人，或许不像他们所想的那么有理有据。即使是在个人层面，这两种饮食的表现之相似是毫无疑问的。

It shows us that the many people, and the many studies, suggesting that we can tell which diets are best for you based on genetics or based on insulin levels might not be right either. Almost all of the studies that backed up such ideas were smaller, of shorter duration or less robust²⁰ in design than this one. Granted, it’s still possible that there might be some gene discovered in the future that makes a difference, but those who think they’ve found it already might want to check their enthusiasm.

它也向我们表明，许多人和许多研究认为我们能根据基因或胰岛素水平来判断哪种饮食对你有益，可能也是不对的。几乎所有支持这些想法的研究都规模较小、时间跨度更短或设计方案鲁棒性不足。诚然，未来仍有可能发现一些能产生影响的基因，但那些觉得自己已经发现了这个基因的人，可能需要再考虑考虑了。

This study was focused mostly on people who were obese, so people looking to lose just a few pounds might benefit more from one diet or the other; we don’t know. It’s also worth noting that the people in this study received significant support on both diets, so the results seen here might not apply to those attempting to lose weight on their own.

这项研究主要关注那些肥胖的人，所以我们不知道想要减掉几磅体重的人会从哪种饮食上获益更多。同样值得注意的是，这项研究的参与者不管采用哪种饮食方式都获得了大量支持，所以它的结果可能并不适用于那些试图自己减肥的人。

You should be wary²¹ of those who tell you that they know what diet is best for you, or that there’s a test out there to tell you the same. Successful diets over the long haul are most likely ones that involve slow and steady changes. The simplest approach — and many have espoused²² it, including Jane Brody recently here at The Times — is to cut out processed foods, think about the calories you’re drinking, and try not to eat more than you intend to.

如果有些人对你说，他们知道什么样的饮食最适合你，或者有个测试能帮你测出来，对此你要保持警惕。缓慢而稳定的改变才最有可能保证长期节食的成功。最简单的方法是减少食用加工食品，留意你从饮料中摄入了多少卡路里，尽量不要吃得比你打算吃的多。很多人都赞成这种方式，包括最近在时报上发表文章的简·布罗迪(Jane Brody)。

The bottom line is that the best diet for you is still the one you will stick to. No one knows better than you what that diet might be. You’ll most likely have to figure it out for yourself.

最重要的是，最适合你的饮食仍然是你能坚持下去的饮食。没有人比你更清楚你最适合哪种饮食。你很可能需要自己去弄清楚。