瑞典研究人员于本周三表示，从小体重超标但未达到肥胖标准的人早亡的几率要比体重正常的人高出三成，这一几率跟每天抽10根烟的人早亡率差不多；而18岁时已确诊为肥胖的人早亡的几率则要比前者高出一倍多，他们面临的早亡危险跟体重正常的长期烟民一样。研究人员还发现，如果一个肥胖的人同时又是个“烟鬼”，那么他早亡的几率则是体重正常又不吸烟的人的五倍。不过，他们也表示，体重过轻的人，尤其是身体质量指数（BMI）低于17的人，早亡率与体重超标或者吸烟人群很接近。因此，这样的研究结果应该得到关注，人们对体重和健康的关系也需要有所了解。

Simply being overweight, but not obese¹, from an early age boosts the risk ofpremature death by a third -- as much as smoking up to 10 cigarettes a day, researchers in Sweden reported Wednesday.

People who are clinically obese by the age of 18 more than double that risk, putting themselves in the same danger zone as long-term heavy smokers⁴ of normal weight, they found.

And combining the two factors accumulates the risk: an obese heavy smoker³, for example, is nearly five times as likely to die prematurely⁵ than a non-smoker who is neither too thin nor too fat.

At least a billion people in the world are overweight, and nearly a third of them are obese, according to the World Health Organisation⁶ (WHO). Obesity⁷ rates have soared over the last three decades, especially among children.

Earlier studies have shown that being excessively fat shortens lifespan and leads to increased rates of chronic⁸ disease such as diabetes⁹ and arteriosclerosis.

But researchers have disagreed sharply up to now on whether being above ideal weight without crossing the line to obesity takes years off one's life.

Nor have previous studies directly compared the impact on mortality of smoking and excess weight.

The study designed by Martin Neovius of the Karolinska Institute in Stockholm goes a long way to settling the debate, and shows clearly for the first time that being too heavy can be as dangerous as smoking a couple of packs a day.

Neovius and colleagues analysed data for 45,000 men who underwent mandatory¹⁰ military conscription tests in Sweden in 1969 and 1970 at the age of 18.

Data included participants' smoking habits, and theirbody-mass index (BMI) -- weight in kilogrammes divided by the square of one's height in meters.

A BMI of 25-to-30 indicates being overweight, while above 30 means one is obese. The range of normal weight is 18.5-to-24.9.

The follow up period was, on average, 38 years. During that time, 2,897 subjects died.

The lowest death rate, as expected, was among non-smokers of normal weight. But researchers were surprised to find that being obese carried a greater risk of premature² death than being a heavy smoker.

Even more startling, however, were the dangers of being overweight.

"What we show is that for the overweight, there is a significantly increased risk of premature death, similar to smoking one-to-ten cigarettes a day," said Neovius in a phone interview.

Two key studies in the United States -- one at the Center for Disease Control and the famous Nurses' Health Study at Harvard -- had arrived at opposite conclusions on this question.

"Our results confirm the Harvard findings," said Neovius, whose research was published in the British Medical Journal.

The two studies are highly complementary, he added. "We find exactly the same in men and they did in women," erasing¹¹ any doubts as to possible differences across the sexes.

The Swedish study did find, however, that being severely¹² underweight -- a BMI of under 17 -- carried about the same risk of early death as being overweight or a light smoker.

Policy makers¹³ should take note of these results, and increase awareness¹⁴ of the risks related to being too fat, or too thin, Neovius said.

"Anti-smoking campaigns have been very successful. But we don't have any good preventative programmes for overweight and obesity," he said of Sweden, adding that the situation elsewhere is comparable.

Vocabulary:

premature death: 夭亡，早亡

BMI: Body-mass index，身体质量指数