THE answer to obesity is obvious: eat less and exercise more. However, years of exhortation have failed to persuade most of those affected actually to do this. In particular, it is much harder to shift surplus lard once it has accumulated than it is to avoid putting it on in the first place. Oddly, though, a convenient mathematical model describing this fact has yet to be widely adopted. But a paper in this week's Lancet, by Kevin Hall of America's National Institutes of Health (NIH) and his colleagues, aims to change that.

【翻译参考】
减肥的方法显而易见，就是少吃多运动。然而，这一方法在过去这么多年中并没有说服大多数的肥胖者去付诸行动。特别是，减去已经堆积起来的脂肪远比避免长出多于脂肪困难得多。奇怪的是，尽管有这样一个的便利的数学模式来描述这一事实，但是它却并没有被广泛接受。但是发表在本周Lancet杂志上的一篇论文却试图改变这一情况。该文是由美国国家卫生研究院的Kevin Hall和他的同事共同撰写完成。

【好词好句】
1. sth fails to do sth
相对应的 success in doing sth
2. have the benefit of sth/doing sth 有......好处， 有利于
不要总是用sth is good for 了
3. account for 考虑到，鉴于
4. it acknowledges that 承认（不过 it is acknowledged that 这个句型更常见）
5. in stages 有阶段性的
6. a will of iron 钢铁般的意志

【summary】
The difficulty of losing weight is captured in a new model.

The conventional rule for slimming, espoused by both the NIH and Britain's National Health Service, has the benefit of simplicity: cut 500 calories each day and lose half a kilo (about a pound) a week. Most experts, though, acknowledge that this rule is too blunt as it fails to account for shifts in the body's metabolism as the kilos pile on. Dr Hall's model tries to do this. It also accounts for baseline characteristics that differ from person to person. Fat and muscle, for example, respond differently to shifts in diet, so the same intake will have one effect on a podgy person and another on a brawny one. The result is a more realistic assessment of what someone needs to do to get slim.