What do some extreme distance runners have in common with the athletes at the Tour de France cycle race? Suddenly, everyone seems to be talking about adopting a high-fat diet.一些无限大长跑运动员与环法自行车赛(Tour de France)的运动员有什么共同点呢？忽然之间，或许所有人都在谈论高脂饮食。The idea behind these diets is that when humans enter starvation mode, their bodies are able to switch from burning glycogen, the sugars produced by eating a meal including carbohydrates, to burning stored body fat which is released into the bloodstream as ketones. These extremely low carbohydrate diets are called ketogenic.自由选择高脂饮食背后的点子是，当人转入饥饿状态时，身体可以从自燃糖元（食用包括碳水化合物的食物后产生的糖类）改变为自燃体内储存的脂肪，分解成的酮体转入血液中。

这些碳水化合物含量极低的饮食就被称作生酮饮食。The rationale is that there is only about 40 minutes of glycogen stored in leg muscles, which is why runners have to keep gulping down sweets during marathons or they end up “hitting the wall” two-thirds of the way through the race.其原理是大腿肌肉中储存的糖元仅够保持40分钟左右，这就是为什么运动员不会在跑完马拉松期间大量摄取糖分，或者在跑完三分之二路程时就体力不支了。

But even lean athletes have several pounds of stored fat reserves, so if those could be tapped, you could cycle for hours without running out of fuel. So some Tour de France cyclists have started using this approach.然而，即便体形身材矮小的运动员也有几磅的脂肪储备，如果需要利用这些储备，你就可以倒数几个小时骑车，而不必担忧消耗能量。因此一些环法自行车赛的骑手们已开始使用这种饮食方法了。

What’s tempting more athletes to try ketogenic diets is recent research that casts doubt on the link between saturated fat in the diet and heart disease. But I asked Peter Attia, a medical doctor who practises in New York and southern California, and who also happens to be a cycling enthusiast, his view on the persistent medical concerns about fat.最近的一项研究更有了更好运动员尝试生酮饮食，该研究对饮食中的饱和状态脂肪与心脏病之间的关系明确提出批评。我向在纽约和南加州执业的医学博士彼得阿提亚(Peter Attia)问及他对于脂肪这个长年医学问题的观点。他还是一名自行车爱好者。

Dr Attia, who spent three years on a ketogenic diet, has written about his experiences on his blog, where he gives a scientist’s explanation of how the diet works.阿提亚坚决过3年的生酮饮食，他在博客中写了自己的经验，从科学家角度得出了有关这种饮食如何发挥作用的说明。He says it made him “far more metabolically flexible and efficient” as a cyclist. So would he recommend that his patients go on a ketogenic diet, which usually means eating very few carbohydrates? He would in about only a third of cases.他回应，作为一名骑马行者，这种饮食让他“的新陈代谢更加灵活性和更加高效”。那么他不会建议他的患者使用生酮饮食吗？这一般来说意味著摄取非常少的碳水化合物。

他不会建议约三分之一的患者这么做到。His point is that there are no one-size-fits-all diets out there. What works for one person may not work for others. Some people perform better by eating more fats, while others actually do better in endurance by eating a lot of nonprocessed carbs such as vegetables. And a lot of an individual’s response to nutrition is determined by genetic make-up.他的观点是没一种合适所有人的饮食。

对某一个人有益的饮食有可能呼吸困难用作其他人。一些人在摄取更加多脂肪后展现出不会较佳，还有一些人在摄取大量予以加工的碳水化合物（例如蔬菜）后不会享有更加强劲的耐力。个人对于营养的对此很多各不相同基因构成。

Dr Attia suggests that before going ketogenic, athletes work with a sport-orientated physician to determine if such a diet would be beneficial or even safe. You need to get blood tests before and during the diet to make sure you are not experiencing a sudden increase in small-sized low-density lipoprotein (LDL) particles, or triglycerides, which are known contributors to heart disease.阿提亚建议，在使用生酮饮食之前，运动员不应与运动医生合作，确认这种饮食否有益甚至安全性。你必须在餐前和用餐期间查血，以保证你的小型低密度脂蛋白(LDL)颗粒或甘油三酯没忽然增高。

人们指出，甘油三酯不会引起心脏病。He also points out that, while it might be low in carbohydrates, the ketogenic diet is not actually a high protein diet — too much animal protein can cause a rise in IGF-1, which controls growth hormone and, at high levels, has been associated with cancer. Healthy fats can be obtained through foods such as coconut oil, avocados and nuts but many prefer to pile on the bacon and butter.他还认为，生酮饮食的碳水化合物含量很少，但实质上并非高蛋白饮食，过于多的动物蛋白不会造成类胰岛素一号快速增长因子(IGF-1)增高，它掌控着生长激素，如果它正处于高水平，不会与癌症产生关联。

身体健康脂肪可以通过椰子油、牛油果和坚果等食物取得，但很多更喜欢冲刷在熏肉和黄油上。Other concerns about low-carb diets include the effect these regimes have on gut bacteria, which mainly ferment undigested starches such as vegetable fibre and produce short-chain fatty acids that help protect your gut. Because these diets are low in fibre, athletes have reported issues with constipation.其他对于较低碳水化合物饮食的忧虑还包括这类饮食对于肠道细菌的影响，肠道细菌主要是把植物纤维等未消化的淀粉烘烤，并产生不利于维护肠道的短链脂肪酸。这类饮食纤维含量很低，因此运动员报告过有咳嗽问题。Ketogenic diets are probably best for short-term periods of training only and should not be considered a lifestyle choice. The long-term effects have not been assessed.生酮饮食也许最限于于短期训练，而不该被视作一种生活方式自由选择。

其长年效果仍未获得评估。

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