什么样的食物会增肥？

One fundamental and unanswered question in obesity research is what kinds of food contribute most to the condition. Experts variously blame， for example， fatty or sugary fare or food that lacks protein， which may prompt us， unconsciously， to overeat. Plenty of anecdotal evidence can be marshaled against any of the culprits， but there has been little long-term， large-scale experimental research on peoples comparative eating habits. It is neither ethical nor practical to have healthy subjects gorge themselves on one diet for years until they are obese.

肥胖研究中一个很根本却一直悬而未解的问题是：什么样的食物最容易导致肥胖？对此问题专家们有各种看法，例如，高脂肪、高糖分或缺乏蛋白质的食物可能会无意识地促使我们暴饮暴食。虽然大量的经验证据可以用来否定那些我们认为会让人发胖的食物，但是关于人们的饮食习惯，却少有长期的、大规模的对比试验研究。因为让健康的人多年暴食一种食物，直到肥胖，这既不道德，也不现实。

It is possible， though， to conduct this sort of experiment on mice. For a diet study published in Cell Metabolism， researchers randomly assigned one of 29 different diets to hundreds of adult male mice. （The scientists hope to include female mice in later experiments.） Some diets supplied up to 80 percent of their calories in the form of saturated and unsaturated fats， with few carbohydrates; others included little fat and consisted largely of refined carbohydrates， mostly from grains and corn syrup. Yet other diets were characterized by extremely high or low percentages of protein. The mice stayed on the same diet for three months—estimated to be the equivalent of roughly nine human years—while being allowed to eat and move about their cages at will. The mice were then measured by weight and body composition， and their brain tissue was examined for evidence of altered gene activity.

但是，对老鼠进行这种实验却是可能的。在《细胞代谢》杂志发表的一项饮食研究中，研究人员将29种不同的饮食随机分配给数百只成年雄性老鼠。（科学家希望在之后的实验中纳入雌性老鼠）有些食物以饱和及不饱和脂肪的形式提供高达80%的卡路里，碳水化合物则很少;另一些则包含少量脂肪，主要由来自谷物和玉米糖浆的精制碳水化合物组成。其他饮食种类的特点是蛋白质含量极高或极低。这些老鼠保持相同的饮食三个月——估计相当于人类饮食的九年——同时允许它们随意进食和在笼子里走动。然后研究人员测量老鼠的体重和身体成分，并对其脑组织进行检查，以寻找基因活性改变的证据。

Only some of the mice became obese—almost every one of which had been on a high-fat diet. These mice showed signs of changes in the activity of certain genes too， in areas of the brain related to processing rewards; fatty kibble made them happy， apparently. None of the other diets， including those rich in sugar， led to significant weight gain or changed gene expression in the same way. Male mice on relatively high-fat diets became obese. The others did not.

只有一些老鼠變得肥胖，这些老鼠几乎都吃的高脂肪食物。在这些老鼠处理奖励信息的大脑区域中，它们的基因活性有改变的迹象，显然，吃高脂肪的粗磨食物会让它们开心。吃其他食物（包括高糖分食物）的老鼠并没有表现出明显的增重或相同的基因表达过程。吃高脂肪食物的雄性老鼠变肥胖了，而其他老鼠并没有。