译者：我用GT翻译，然后快读一遍（纠正明显的错）。没有时间追求“信、达、雅”。

译者：我从2018年6月开始了“9-5 diet” 。每天从上午9点开始吃东西；但是，不要在晚上5点以后吃东西。也就是16:8 diet；即有16个小时不进食。有兴趣的可以点开：

https://blog.sciencenet.cn/blog-306792-1209375.html

间歇性禁食提供了非常诱人的希望，即改变进餐时间而不是改变膳食本身对你的健康有好处。 但是间歇性禁食的注意事项有哪些呢？

间歇性禁食因其减肥和健康益处而受到名人和首席执行官的拥护。 就连英国首相里希·苏纳克 (Rishi Sunak) 也承认，每周都会先进行 36 小时的禁食。 虽然有证据表明禁食可以帮助我们的身体修复，或许还可以延长我们的寿命，但这可能不是减肥的最佳方法；营养师敦促在实行减餐之前要小心。

间歇性禁食是一种限时饮食方式，禁食者在一天的最后一顿饭和第二天的第一顿饭之间留出很长的时间间隔，也就是将一天中的进餐时间压缩到较短的时间。 通常，禁食者会尝试留出 16 小时不进食的时间，只是在 8 小时的时间窗口内进食。 间歇性禁食并不是唯一一种限时饮食。 其他人喜欢 5:2 饮食（其中节食者五天吃正常量的食物，然后两天只吃平常卡路里摄入量的 25%），更多地关注消耗的食物量，而不是两餐之间的间隔时间。

“限时饮食是一种减肥工具，但这不是我最喜欢的方法，”伦敦咨询公司 The DNA Dietitian 的创始人雷切尔·克拉克森 (Rachel Clarkson) 说。 “你减少了卡路里，但你没有了解你摄入体内的食物所带来的基本行为变化。”

克拉克森说，在不了解健康饮食的情况下，人们停止禁食后体重会再次增加。 “如果这意味着你感到饥饿和受到限制，那么第二天你可能会吃得过多。”

因此，间歇性禁食对于寻求减肥的人来说可能不是正确的方法，但可能还有其他原因需要改变你的饮食模式。 禁食与一种称为自噬的过程有关，自噬因其潜在的健康益处而引起了人们的广泛关注。

自噬是身体开始回收细胞内结构的过程，包括储存 DNA 的细胞核、合成细胞用作能量的化学物质的线粒体，以及清除细胞中废物的溶酶体。 在此过程中，细胞可以去除失效的结构，释放出新的原材料，从而可以构建新的细胞结构。 一些新原材料可用于制造细胞保护蛋白，进一步延长细胞的寿命。

人们对自噬是否可以延长整个生物体的寿命也很感兴趣——尽管到目前为止，这一现象只在动物身上得到了验证，比如 1 毫米长的线虫和小鼠，而没有在人类身上得到验证（受抑制的自噬也与早发性老化有关）。 在对人类间歇性禁食进行纵向研究之前，现在说它会延长我们的寿命还为时过早。

但是，其他动物研究已将自噬与免疫系统记忆的改善联系起来。 自噬对于维持细胞健康至关重要，这一事实也引起了人们对其在癌症抑制中的作用的兴趣。 除了延长寿命之外，可能还有更多原因让人们对自噬感兴趣。

对于我们大多数人来说，自噬发生在睡眠中，但运动和饥饿也会引起自噬。 控制禁食有助于触发它吗？

与限制热量饮食（也与长寿有关）不同，间歇性禁食的目的是增加一天最后一顿饭和第二天第一顿饭之间的间隔时间。 （理论上，间歇性禁食可以摄入与正常情况相同量的卡路里，尽管克拉克森说大多数人实际上会稍微减少摄入量。）这可能有助于促进自噬，但要了解我们应该如何看待禁食后发生在我们身上的事情 我们吃。

“当你在 19:00 停止进食时，你在 22:00 之前仍将处于‘吃饱状态’，因为你仍在消化营养，”克拉克森说。 “饮食中的任何碳水化合物都会为你提供充足的葡萄糖，这是我们的优质燃料来源，持续几个小时。”

进食状态是指你的身体使用血液中的葡萄糖作为能量来源。 一旦这种能量来源耗尽，身体就会进入分解代谢状态——通常在进食后三个小时左右。 在这个阶段，储存在肝脏和肌肉中的糖原被分解成葡萄糖。 当我们耗尽糖原储备时，身体就会从葡萄糖转变为酮，酮是在肝脏中由脂肪酸产生的。 正是在这个阶段，即一个称为酮症的阶段，自噬被触发。

“我们不知道何时从葡萄糖转向酮，”克拉克森说。 “这取决于很多事情； 遗传、健康、生活方式。 你有多少糖原将取决于你吃了多少和燃烧了多少能量。”

高碳水化合物饮食的人可能永远不会超越分解代谢状态，因为他们总是有糖原的储备供应。 然而，采用低碳水化合物饮食并经常锻炼的人可能会很快完成这个过程（“酮饮食”，即你戒掉几乎所有碳水化合物以维持低血糖水平和糖原储存，以同样的方式工作） 。 “我会放弃间歇性禁食来减肥，如果你想采用它，请考虑一下它对健康的好处，”克拉克森说。

如何禁食

“要禁食，你必须降低饥饿感，”克拉克森说。 当胃饥饿素（一种从胃中释放的激素）触发下丘脑中另外两种激素（NPY 和 AgRP）的产生时，我们就会感到饥饿。

虽然这三种激素会产生饥饿感，但还有多种激素会抑制饥饿感。 有时被称为“饱腹感激素”，其中一个关键激素是瘦素，它从脂肪细胞中释放出来，以抑制生长素释放肽的产生——基本上告诉身体“这里有脂肪可以燃烧”。

生长素释放肽有时被称为短期饥饿反应，因为它在胃空且胃壁压力较小时释放。 喝水可以在一定程度上克服它。 与此同时，瘦素可以长期发挥作用。

“我们的饥饿激素受到很多因素的调节，遗传就是其中之一，”克拉克森说。 “但是想想与我们的胃和消化道相连的神经——如果你的胃没有膨胀，你的身体就会认为它饿了。” 她补充说，保持水分可以帮助缓解早期的饥饿感，直到你的身体适应为止。 “最初几周会很艰难，但你会习惯的。”【译者：试一下，如果你“感觉饿了”，先喝一杯水或者是淡茶。】

对于大多数人来说，酮症发生在进食后 12-24 小时，因此，如果你在 18:00 至 20:30 之间吃晚饭，进食状态将在 21:00 至 23:30 之间结束，酮症和自噬可能会在 06 点发生 :00 至次日早上 08:30。 “但大多数人在晚餐后坐下来打开一包其他东西（食物），”克拉克森说。 “零食或含糖饮料和啤酒可以将进食状态延长三个小时。 如果你在 21:30-22:00 吃完零食，联邦状态将被带到 01:00-03:00，”她说。 这可能意味着在你下次进餐之前永远不会发生酮症。

“如果你能做出明智的决定，提前一小时吃晚餐并且不吃零食，那么你可能会在早上进入酮症状态，而不是那些吃高碳水化合物晚餐和零食、在 06 ：00点起床的人，永远不会进入那种状态，”她说。 克拉克森建议从周日晚上早点吃东西开始，或者（第二天）晚一小时吃早餐；然后从那里开始，从每周1～2天开始。

通过谨慎的方法，间歇性禁食可能会帮助你的身体进行自我修复和恢复。 自噬似乎会随着年龄的增长而下降，因此在以后的生活中增强自己可能会有用。 但请注意，这可能不是正确的减肥策略，而且均衡饮食是无可替代的。

本文于 2024 年 1 月 31 日更新，包含有关 Rishi Sunak 禁食的详细信息。 它最初于 2022 年 1 月 11 日发布。

本文中的所有内容仅供一般参考，不应替代医疗保健专业人员的医疗建议。 如果你怀孕了或患有糖尿病等健康问题，并且正在考虑间歇性禁食、计划长期禁食，并且禁食时不应避免喝水，你应该咨询你的医生或医疗保健专业人员。

The benefits of intermittent fasting the right way

https://www.bbc.com/future/article/20220110-the-benefits-of-intermittent-fasting-the-right-way

31st January 2024, 04:02 HST

By William Park

Features correspondent

Intermittent fasting offers the tantalising promise that changing mealtimes, and not the meals, can be good for you. But what are the dos and don’ts of eating less frequently?

Intermittent fasting is championed by celebrities and chief executives alike for its weight loss and health benefits. Even Rishi Sunak, the British Prime Minister, has admitted to starting each week with a 36 hour long period of fasting. While there is promising evidence that fasting can help our bodies repair and perhaps extend our lifespans, it might not be the best approach for losing weight, and dietitians urge caution before cutting out meals.

Intermittent fasting is a type of time-restricted diet in which fasters leave a long gap between their last meal of one day and first of the next, compressing their meals into a shorter period during the day. Typically, fasters try to leave a gap of 16 hours without food and eat during an eight-hour window. Intermittent fasting is not the only type of time-restricted diet. Others like the 5:2 diet (in which dieters eat a normal amount of food for five days before two days of eating only 25% of their usual calorie intake) focus more on the amount of food consumed, rather than the time between meals.

“Time-restricted feeding is used as a weight loss tool, but it’s not my favourite approach,” says Rachel Clarkson, founder of London-based consultancy The DNA Dietitian. “You reduce calories but you don’t learn the essential behaviour change around what you're putting into your body.”

Clarkson says that without learning what a healthy diet looks like people gain weight again when they stop fasting. “If it means you are feeling starved and restricted then the next day you might over-eat.

So, intermittent fasting might not be the right approach for people seeking weight loss, but there might be other reasons to change your eating patterns. Fasting is linked to a process called autophagy, which is attracting a lot of interest for its potential health benefits.

Autophagy is the process by which the body starts to recycle the structures inside its cells, including the nucleus, where DNA is stored, the mitochondria, which synthesise the chemical our cells use for energy, and lysosomes, which remove waste from our cells. In doing so, the cell can remove defunct structures, freeing up new raw materials from which new cellular structures can be built. Some of the new raw material might be used to make cell-protective proteins that further extend the lifespan of cells.

There is interest in whether autophagy can increase the lifespan of whole organisms, too – though so far this has only been replicated in animals, like 1mm-long nematode worms and mice, and not humans (inhibited autophagy has also been linked to early-onset ageing). Until there are longitudinal studies of human intermittent fasters, it is too soon to say that it will extend our lifespans.

But, other animal studies have linked autophagy to improvements in immune system memory. The fact that autophagy is essential to maintain cell health has also generated interest in its role in cancer suppression. There might be more reasons than increasing lifespan to take interest in autophagy.

For most of us, autophagy occurs in our sleep, but it is also brought on by exercise and starvation. Could controlled fasting help to trigger it?

Unlike calorie-restrictive diets (which have also been linked to longevity), the purpose of intermittent fasting is to increase the amount of time between the last meal of one day and the first of the next. (In theory, an intermittent faster could eat the same amount of calories as normal, though in practice Clarkson says most people reduce their intake slightly.) This could help to promote autophagy, but to understand how we should look at what happens to us after we eat.

“When you stop eating at 19:00 you will still be in the ‘fed state’ until 22:00 because you will still be digesting nutrients,” says Clarkson. “Any carbohydrates in your diet will give you a nice supply of glucose, our premium source of fuel, for a few hours.”

The fed state is when your body uses glucose in your blood as its source of energy. Once this energy source is used up, the body switches into a catabolic state – usually around three hours after eating. In this phase, glycogen stored in the liver and muscles is broken down into glucose. When we have depleted the glycogen stores, the body switches from glucose to ketones, which are made in the liver from fatty acids. It’s at this point, a stage called ketosis, that autophagy is triggered.

“We don’t know exactly when we shift from glucose to ketones,” says Clarkson. “It depends on so many things; genetics, health, lifestyle. How much glycogen you have will be based on how much you have eaten and how much energy you have burned.”

Someone who has a high-carb diet might never move beyond the catabolic state as they will always have a reserve supply of glycogen. However, someone with a low-carb diet and who regularly exercises might move through it very quickly (the “keto diet”, in which you cut out almost all carbs to maintain low blood glucose levels and glycogen stores, works in the same way).  “I would move away from intermittent fasting for fat loss, and if you want to adopt it think about the health benefits,” says Clarkson.

How to fast

“To fast you have to downregulate the feeling of hunger,” says Clarkson. Hunger is felt when ghrelin, a hormone released from our stomach, triggers the production of two other hormones, called NPY and AgRP, in the hypothalamus.

While these three hormones generate feelings of hunger, there are a multitude more that suppress it. Sometimes called the “satiety hormones”, one of the key ones is leptin which is released from fat cells to suppress the production of ghrelin – basically telling the body "there is fat here that you can burn".

Ghrelin is sometimes called the short-term hunger response because it is released when the stomach is empty and there is less pressure on the stomach wall. It can be overridden to a certain extent by drinking water. Leptin meanwhile works over the long term.

“Our hunger hormones are regulated by many things, genetics being one of them,” says Clarkson. “But thinking about the nerves that are attached to our stomach and digestive tract – if your stomach is not distended your body will think it is hungry.” She adds that staying hydrated can help with the early feelings of hunger until your body has adjusted. “The first couple of weeks will be tough, but you get used to it.”

For most people, ketosis occurs 12-24 hours after eating, so if you have your evening meal between 18:00 and 20:30, the fed state would end between 21:00 and 23:30 and ketosis and autophagy might occur by 06:00 to 08:30 the following morning. “But the majority of people are sitting down and opening a packet of something else after dinner,” says Clarkson. “Snacking or sugary drinks and beer extend the fed state for three hours. If you finish snacking at 21:30-22:00, the fed state is being taken to 01:00-03:00,” she says. This might mean ketosis never occurs before you next have a meal.

“If you can make the informed decision of eating the evening meal an hour earlier and not snacking, you may be getting into that ketosis state by morning, versus someone who is having the high-carb evening meal and snacking, waking up at 06:00 and never getting into that state,” she says. Clarkson suggests starting by eating earlier on a Sunday evening, or having breakfast an hour later and starting from there, building up from one or two days each week.

With a careful approach, intermittent fasting might help your body to perform its own repairs and recoveries. Autophagy appears to decline with age, so giving yourself a boost later in life might be useful. But be aware that it might not be the right strategy for weight loss, and there is no replacement for a balanced diet.

This article was updated on 31 January 2024 to include detail about Rishi Sunak's fasting. It was originally published on 11 January 2022. 

All content within this article is provided for general information only, and should not be treated as a substitute for the medical advice of healthcare professionals. You should speak to your doctor or healthcare professional if you are pregnant or have a health condition such as diabetes and are considering intermittent fasting, are planning to fast long-term, and you should not avoid fluids while fasting.