哈佛專家說你錯了 胖並非吃太多

David Ludwig often uses an analogy when he talks about weight loss: Human beings are not toaster ovens. If we were, then the types of calories we consumed would not matter, and calorie counting would be the most effective way to lose weight.

談到減肥，戴維·路德維希(David Ludwig)經常會打這麼一個比方：人體可不是個烤箱喲。如果是烤箱的話，那我們不管吃何種食物都無關緊要，而且計算熱量卡路里數會是最有效的減肥方法。

Dr. Ludwig, an obesity expert and professor of nutrition at the Harvard T.H. Chan School of Public Health, argues that weight gain begins when people eat the wrong types of food, which throws their hormones out of whack and sets off a cycle of cravings, hunger and bingeing. In his new book, “Always Hungry?,” he argues that the primary driver of obesity today is not an excess of calories per se, but an excess of high glycemic foods like sugar, refined grains and other processed carbohydrates.

路德維希博士是哈佛大學公共衛生學院(Harvard T.H. Chan School of Public Health)的肥胖症專家和營養學教授，他認爲，人要是吃錯了東西，就會引發激素紊亂，陷入“想吃—飢餓—暴飲暴食”的惡性循環，結果就是體重開始增加。在其新書《總覺得餓嗎？》(Always Hungry?)中，他提出，如今，肥胖症的主要原因並非是攝入了過多的熱量本身，而是食用了過量的高升糖指數食物，如糖、精製穀物和其他經加工的碳水化合物等。

Recently, we caught up with Dr. Ludwig to talk about which foods act as “fertilizer for fat cells,” why he thinks the conventional wisdom on weight loss is all wrong, and long-term strategies for weight loss. Here are edited excerpts from our conversation.

近日，我們採訪了路德維希博士，請他談談哪些食物是“脂肪細胞的肥料”，爲什麼他認爲關於減肥的傳統觀念全是錯的，以及減肥的長期策略等。以下是我們的對話節錄。

Q. What is the basic message of your book?

問：請問你這本新書的主旨是什麼？

A. The basic premise is that overeating doesn’t make you fat. The process of getting fat makes you overeat. It may sound radical, but there’s literally a century of science to support this point. Simply cutting back on calories as we’ve been told actually makes the situation worse. When we cut back on calories, our body responds by increasing hunger and slowing metabolism. It responds in an effort to save calories. And that makes weight loss progressively more and more difficult on a standard low calorie diet. It creates a battle between mind and metabolism that we’re doomed to lose.

答：這本書的基本前提是，並非是暴飲暴食讓你發胖，而是發胖的過程會令你過量進食。這聽起來可能有些過激，但我們可以毫不誇張地說，最近一個世紀以來的科學足以支持這一觀點。那些要我們減少熱量攝入的告誡其實起了反作用。一旦熱量攝入減少，我們的身體就會做出反應，一方面增加飢餓感，另一方面則減緩新陳代謝的速度。也就是說，它在儘可能地節約熱量。正因爲此，人們往往會發現在堅持標準的低熱量飲食時，減肥變得越來越困難了。在這場意志與新陳代謝之間的鬥爭中，我們註定會是失敗者。

Q. But we’ve all been told that obesity is caused by eating too much. Is that not the case?

問：但是，人們不是一直都在說，肥胖是因爲吃得太多造成的麼？難道事實並非如此？

A. We think of obesity as a state of excess, but it’s really more akin to a state of starvation. If the fat cells are storing too many calories, the brain doesn’t have access to enough to make sure that metabolism runs properly. So the brain makes us hungry in an attempt to solve that problem, and we overeat and feel better temporarily. But if the fat cells continue to take in too many calories, then we get stuck in this never-ending cycle of overeating and weight gain. The problem isn’t that there are too many calories in the fat cells, it’s that there’s too few in the bloodstream, and cutting back on calories can’t work.

答：我們總覺得肥胖是一種過剩，但它實際上更近似飢餓的狀態。如果脂肪細胞總是過度地儲存熱量，大腦就得不到足夠的熱量來確保新陳代謝正常運行。爲了解決這個問題，大腦讓我們產生了飢餓感，於是我們吃下了超量的食物，暫時感覺好過了一些。但如果脂肪細胞繼續囤積過多的熱量，我們就會被困在無休無止的“暴飲暴食—體重增加”的循環當中。所以問題並不在於脂肪細胞中的熱量過多，而是血液中的熱量太少。這就是靠減少熱量攝入無法成功減肥的原因。

Q. That’s very different from the conventional wisdom that weight loss boils down to calories in, calories out.

問：這與將減肥歸結爲熱量收支的傳統觀念有很大差異呢。

A. Yes. An analogy would be like trying to treat a fever with an ice bath. Imagine going to the hospital with a very high fever, and the doctor says, “Fever is just a problem of heat balance – too much heat in the body, not enough heat leaving the body.” That’s true from a physics standpoint. So the doctor decides to put you in an ice bath. That will work temporarily. An ice bath will break your fever. But imagine what’s going to happen. Your body is going to fight back furiously with severe shivering and blood vessel constriction and you’ll feel miserable. You’ll want out of that ice bath as soon as possible. For that reason, ice baths are not a popular treatment for fever.

答：是啊。我們可以拿“試圖用冰浴退燒”來做個類比。想像一下，你因爲發高燒而去醫院就診，醫生跟你說：“發燒只是熱平衡的問題——體內熱量過多，散熱不足。”從物理學的角度來看，這倒是也沒錯——於是醫生決定讓你接受冰浴。暫時看來，這當然會有效，冰浴確實能讓你的體溫降低。但是，請想像一下接下來會發生什麼。你的身體很快會對低溫環境做出反擊，你劇烈顫抖，血管收縮，你覺得苦不堪言，渴望儘快從那冰浴中逃離。所以，醫生根本不會把冰浴作爲退燒的常用治療手法。

Q. So in this analogy, how do you treat the underlying cause?

問：那麼，仍然借用這個類比來說，你認爲應如何針對病因加以治療呢？

A. A much more effective approach is to lower the body’s temperature set point, which is done with medicine like aspirin. Put biology on your side by eating the right way, and weight loss occurs naturally as a fever would break if you treat the underlying cause of the fever.

答：利用阿司匹林等藥物降低體溫調定點是較爲有效的方法。正如你想要退燒，就要治療發燒的根本原因一樣，當你食用正確的食物時，生物學規律就會自然而然地幫你減肥。

Q. If it’s not overeating, then what is the underlying cause of obesity?

問：如果肥胖的根本原因不是暴飲暴食，那又是什麼呢？

A. It’s the low fat, very high carbohydrate diet that we’ve been eating for the last 40 years, which raises levels of the hormone insulin and programs fat cells to go into calorie storage overdrive. I like to think of insulin as the ultimate fat cell fertilizer.

答：是近40年來我們的低脂肪但碳水化合物非常高的飲食，它會提高胰島素的水平，促使脂肪細胞過度儲存熱量。我喜歡把胰島素稱爲脂肪細胞的首要增肥劑。

When someone with Type 1 diabetes first comes to attention, their blood sugar is high because they can’t make enough insulin. They invariably have lost weight. They may be eating 5,000 calories a day, and they’re still losing weight. You can’t gain weight without insulin. The opposite is also true. If you give someone with diabetes too much insulin, they will inevitably gain weight. Insulin programs the body to store calories, and most of those calories get stored in the fat cells. If you’ve got too much insulin, you’re going to store too many calories. This has been very well established scientifically.

當I型糖尿病剛剛出現時，病患的身體因爲無法制造出足夠的胰島素，血糖總是很高。他們幾乎無一例外都非常消瘦。雖然他們每天可攝入多達5000卡路里的熱量，體重仍在不斷地減輕。沒有足夠的胰島素，你就長不胖。反之亦然。要是你給某個糖尿病患者注射了過量的胰島素，他就會不可避免地增加體重。胰島素促使身體存儲熱量，這些熱量大多會以脂肪的形式儲存在脂肪細胞裏。如果你體內的胰島素過多，你就會儲存過多的熱量。這些都已經得到了科學的充分證實。

Q. How do you get your obese patients to lower their insulin?

問：那要如何才能降低肥胖症患者的胰島素水平呢？

A. The quickest way to lower insulin is to cut back on processed carbohydrates and to get the right balance of protein and fat in your diet. A high fat diet is really the fastest way to shift metabolism. It lowers insulin, calms fat cells down and gets people out of the cycle of hunger, craving and overeating.

答：降低胰島素的最快辦法是少吃經加工的碳水化合物，並均衡攝入蛋白質和脂肪。其實，高脂肪飲食是改變新陳代謝的最迅速的方法。它可以降低胰島素水平，讓脂肪細胞不再忙於囤積脂肪，人就擺脫了“飢餓—食慾—暴飲暴食”的怪圈。

Q. It sounds like the program you’re advocating is the Atkins diet.

問：這麼說，你崇尚阿特金斯飲食(Atkins diet)？

A. No, this is different. The Atkins diet is a very low carbohydrate diet, which in its classic form means you can’t eat much fruit let alone any other carbohydrate. Many people don’t require – and are probably unwilling to sustain – the rigors of a very low carbohydrate diet. I think that except for people with already very severe metabolic problems like Type 2 diabetes, such restrictive regimens are not usually necessary.

答：不，我推薦的減肥方案與之不同。阿特金斯飲食是碳水化合物含量非常低的飲食。在典型的阿特金斯飲食中，你不能吃太多的水果，更遑論其他的碳水化合物。很多人並不需要——而且很可能也不願意維持這樣嚴格的低碳水化合物飲食。我認爲，只要你沒有II型糖尿病之類非常嚴重的代謝問題，一般無需執行這種限制太多的治療方案。

Q. How does this program work?

問：那你的治療方案是怎樣的？

A. Our program has three phases. First we tell people to give up processed carbohydrates, added sugars and all grain products for two weeks. The carbohydrates you eat should be a range of nonstarchy vegetables, fruits and beans. After two weeks, we reintroduce whole kernel grains, potatoes – except for white potatoes – and a little bit of added sugars. You do this until your weight comes down to a new, lower set point. It could be a few weeks, or it could be many months for someone who has a more significant weight problem.

答：我們的治療方案分爲三個階段。首先，我們要求人們在兩週內完全不食用經加工的碳水化合物、添加糖和所有的穀物製品。你可以吃碳水化合物，但應該選擇各種非澱粉類蔬菜、水果和豆類。兩週後，你可以在膳食中添加全粒穀物、薯類（土豆除外）和一點點的添加糖。請堅持這樣的飲食，直到你的體重下降到一個新的、較低的調定點上。這可能需要幾個星期，對於體重問題較爲嚴重的人甚至需要數個月的時間。

Q. Where do you stand on saturated fat?

問：你對飽和脂肪怎麼看？

A. I think throughout the public health establishment we’re recognizing that saturated fat isn’t Public Health Enemy No. 1. But it’s also not necessarily a health food. There are many different kinds of saturated fats, and each of these has different effects on the body. But when you reduce processed carbohydrates and your insulin levels decrease, the saturated fat you consume burns faster and it doesn’t stick around the body as long.

答：我認爲，整個公共衛生界正逐漸認識到飽和脂肪並非公共健康的頭號公敵——但它也未必是健康食品。飽和脂肪有很多不同的種類，每種對人體各有不同的影響。不過，當你減少經加工的碳水化合物的攝入量，胰島素水平下降後，你燃燒攝入的飽和脂肪的速度就會加快，它就不會一直賴在你的身體裏。

We have to stop thinking about saturated fat as either just good or bad. Our meal plan is based on whole natural foods, which include saturated fat. But we make sure to balance that with lots of mono- and polyunsaturated fats like olive oil, nuts, avocado and flaxseed oil.

我們不應再單純地考慮飽和脂肪是好是壞。我們的膳食計劃的基礎是全天然食品，其中包括了飽和脂肪。但必須確保我們在攝入飽和脂肪的同時，攝入大量的單不飽和脂肪和多不飽和脂肪，如橄欖油、堅果、鱷梨和亞麻籽油，讓這兩者之間達到均衡。

Q. Ultimately, what do you want people to take away from this book?

問：最後，你希望讀者從這本書中學到什麼？

A. Until we address the underlying drivers of weight gain – which are fat cells stuck in calorie storage overdrive – we are going to be in a battle between mind and metabolism that we just can’t win. Cutting back on calories won’t do it. That doesn’t change biology. To change biology, you have to change the kinds of foods you’re eating.

答：脂肪細胞過度囤積熱量是我們體重增加的根本原因，如果不能解決這個問題，我們就註定要在意志與新陳代謝之間的戰鬥中一敗塗地。減少熱量攝入達不到這個目標，它不會改變你的生理狀態；而要改變生理狀態，你必須改變你的食物種類。