Take your height in metres, square it, then divide it by your weight in kilograms. That's how you calculate your body mass index, or BMI. If it's between 18 and 25, your weight is healthy. If it's over, it isn't. So far, so simple. BMI has become a popular metric for people to check their health.把你的身高（以米为单位）平方，然后用这个数去除以你的体重（以千克为单位）。这就是计算你的身体质量指数（BMI）的方法。如果BMI介于18到25之间，你的体重被认为是健康的；如果高于这个范围，则不健康。到目前为止，这很简单。BMI已经成为人们检查自身健康状况的一个常用指标。

On a population level, data backs this up. People with a high BMI are statistically more likely to develop conditions such as hypertension, diabetes, arthritis, and some types of cancer along with other health problems. Checking BMI could be a way for people to easily assess their health and decide if they need to make any lifestyle changes.从人群层面来看，数据支持这一点。统计显示，BMI较高的人更容易出现高血压、糖尿病、关节炎以及某些类型的癌症等健康问题。检查BMI可以让人们更容易评估自身健康状况，并决定是否需要作出生活方式上的改变。

However, BMI does not give the full picture. It's known that it's less accurate for some groups of people, such as children, the elderly or athletes. The measure was devised in the 19th Century by a Belgian mathematician, and this may be why the figures are more accurate for Europeans than other ethnicities. There are also several important factors that it doesn't measure. Someone who is very active may have significant weight from muscle. BMI doesn't differentiate between this or the visceral fat that is linked with negative health outcomes. It doesn't account for the range of nutrients or the level of cholesterol in someone's diet. What this means is that people can have a high BMI and be relatively healthy, while others may have a low BMI but be unhealthy.然而，BMI并不能提供全貌。众所周知，它对某些群体的准确度较低，比如儿童、老年人或运动员。BMI由一位比利时数学家在19世纪提出，这可能也是它对欧洲人比对其他种族更准确的原因。此外，还有一些重要因素是它无法衡量的。一个经常锻炼的人可能因为肌肉较多而体重偏高，而BMI无法区分肌肉重量与对健康不利的内脏脂肪。它也无法衡量一个人的营养摄入结构或胆固醇水平。也就是说，有些人BMI较高但相对健康，而另一些人BMI较低却并不健康。

The simplicity of BMI is attractive, it's also very visible and fits with society's perception of the importance of weight. However, dependence on it as an indication of health can cause stigma. People can feel judged because of their weight. This sometimes leads people to avoid going to the doctors if they know they're likely to be questioned on it. While BMI may be a useful measure, experts remind us that it should always be considered alongside other measures, such as blood pressure, blood sugar level, cholesterol level and others.BMI的简单性很吸引人，它也很直观，并且符合社会对体重重要性的普遍看法。然而，把它当成健康的主要指标可能会让人感到被污名化，人们可能因为体重而感到被评判。这有时会导致一些人因为害怕被询问体重而避免看医生。虽然BMI是一个有用的指标，但专家提醒我们，它应该与其他指标一起考虑，例如血压、血糖、胆固醇水平等。