體重的調定點 Understanding Set-Point Weight

我們很難準確地解釋減重和保持體重背後的原理。為什麼減掉的體重總是會反彈？讀了本文，你就明白。

Finding the right words to clearly explain the complicated science of weight loss and maintenance can be tricky. Use these ideas to educate clients—and yourself—on why lost pounds keep coming back.

人類有自己固有的一套模式來對抗節食。科學家發現：如果沒有長期的體重維持規劃，已經減掉的10%甚至更多的體重會在5年以內反彈回來。（Montesi et al. 2016）

Humans are hardwired to resist dietary restrictions. Science bears this out: In the absence of an ongoing weight maintenance program, half of the people who lose 10% or more of body weight gain it all back within 5 years or so (Montesi et al. 2016).

人們過去常常將這一現象歸因於懶惰或者缺乏飲食原則，然而這一解釋並不適用於所有人。越來越多的證據顯示我們的身體會毫不留情地「調整」體重的過度減少，並回到我們的「初始」體重。體重調定點的科學機制告訴我們，要將焦點從減輕體重值轉移到更健康的生活方式以及體重的維持上面去。

It used to be easy to blame this phenomenon on laziness or lack of dietary discipline. But that explanation isn』t persuasive anymore because of growing evidence that our bodies have a relentless drive to 「correct」 excessive weight loss and return to a 「set-point」 weight. Indeed, the science of set-point weight suggests we may need to shift our focus away from weight loss and toward healthier living and weight maintenance over time.

什麼是體重調定點？它對我們的健康及減重來說有什麼影響？作為健身行業人員，我們要能夠向客戶解釋清楚這些問題。關於體重調定點，你需要明白：

Fitness professionals can play a pivotal role in educating clients about set-point weight and its effect on wellness and weight loss. To make this happen, you must understand

• 人體對節食是如何應答的；
• how the human body responds to dietary restrictions;
• 為什麼身體會自然地回到調定點體重；
• why the body naturally reverts to a set-point weight; and
• 如何說服客戶改變他們關於減重的觀念。
• how to convince clients to shift their perceptions on weight loss.

了解體重調定點這一概念，是幫助客戶擺脫體重總是反覆反彈這一怪圈的第一步。

Educating yourself on set-point weight is the first step toward helping your clients escape the seemingly never-ending cycle of losing and regaining weight.

• 當我們節食時，發生了什麼？

What Happens When We Diet

那句廣為流傳的減肥口號——「管住嘴，邁開腿」——其實是對減重的一個誤導，它並沒有考慮體重調定點這個因素。看看它把減重這件事兒說得有多簡單吧：

The persistence of the simplistic 「eat less, move more」 weight loss mantra is a nagging reminder of widespread misconceptions about the realities of set-point weight. Consider how much this advice exaggerates the ease of weight loss:

燃燒額外的3500卡路里的能量會減輕1磅（約0.9斤）的體重，1年就可能減輕52磅（約47.2斤）的體重，這是一個很驚人的重量。而要實現它只需要每天形成500卡路里的能量缺口就行，比如在運動上多消耗250卡路里，在飲食上少攝入250卡路里。

Supposedly, burning an extra 3,500 calories will trim 1 pound of body weight—potentially yielding a whopping 52-pound weight loss in a year. All it takes is a 500-calorie deficit every day—250 more calories of exercise and 250 fewer calories of food, for instance.

然而這只是理想狀態，現實生活中很難實現。這方法在一開始時當然會很有效果，特別在減重最初的6個月內，製造能量缺口會使體重以肉眼可見的速度下降。之後，不管人們如何堅持他們的「健康的」生活習慣，總會發生一些變數。

Yet somehow this math never seems to translate to real life. Sure, it may work at first. Consistent attention to creating a calorie deficit can make weight seem to peel away—especially over the first 6 months. But then something changes, no matter how well people stick to their new habits.

體重開始慢慢地反彈，這就形成了我們在相關研究和客戶體重記錄中常常能看到的 「體重對號曲線」（見圖1）。

The weight starts to slowly (then not so slowly) creep back on. This creates the classic 「weight loss check mark」 (see Figure 1) we so often see in research studies and in our clients』 weight loss journeys.

我們並沒有了解體重調定點的全部，但我們知道在飲食不足或者飲食過量的狀態下，我們的身體會觸發一系列代謝及內分泌改變機制，進而影響體重的維持。知道了這一機制，有助於我們向客戶傳遞體重調定點這一概念，從而讓他們更好地知道怎麼實現減輕體重、維持體重。

We don』t know everything about set-point weight, but we do know that habitual under- or overfeeding triggers metabolic and hormonal changes that have a profound influence on dieters』 ability to keep weight off. When you understand how these mechanisms work, it will be easier to convey the concept to your clients, thus giving them a better chance to comprehend the realities of their lifelong weight loss and weight maintenance journey.

• 為什麼身體要定一個體重調定點

Why the Body Targets a Set-Point Weight

人類的身體會自然地維持98.6華氏攝氏度（37攝氏度）的穩定體溫。科學家們認為體重調定點與體溫的設定有異曲同工之妙。當一個人的體重達到了調定點（也叫習慣性或者防禦性體重），不管飲食如何波動，他的身體都會調整他的代謝率來維持體重。

The human body naturally strives for a stable temperature of 98.6 degrees. Scientists now believe it does much the same with body weight. Once a person reaches a set-point weight—also called 「customary」 or 「defended」 weight—the body tweaks its metabolic rate to maintain that weight despite dietary fluctuations.

當我們控制能量攝入（即節食）時，為了到達調定的體重，我們的身體會產生飢餓感，同時減少能量消耗。對於遠古人類來說，為了應對食物不足，這一機制是有用的。但是在我們現在這個食物充足，充滿美食誘惑的時代，這一機制就顯得有點雞肋了。

When we restrict calorie intake, the quest for set-point weight makes hunger rise and resting energy expenditure fall. That worked fine for early humans who faced long stretches of food scarcity. It』s less useful in our current era of food abundance and continual temptations to eat highly palatable salty, sugary and calorie-dense foods.

體重調定點到底有多強大？一項以超級減肥王（The Biggest Loser）的參賽者為對象的研究，通過對他們減肥前、減肥後即刻以及減肥後6年後的狀態進行研究，發現他們的代謝率大大地降低。即使一些人保持較活躍的日常體力活動，代謝率依然處於較低的水平(Fothergill et al. 2016)。其他的研究發現，減肥一年後內分泌改變依舊存在，增加飢餓感，降低代謝率(Sumithran et al. 2011)。

How strong is the drive for set-point weight? A research project targeted competitors in The Biggest Loser, studying them before weight loss, immediately afterward and then 6 years later. Their metabolic rates dramatically decreased and stayed that way even though the participants remained physically active (Fothergill et al. 2016). Other studies learned that hormonal changes that increase hunger and decrease metabolic rate persist even a year after weight loss (Sumithran et al. 2011).

研究表明，相比對照組中的受試者，實驗組中體重降低的受試者的靜息代謝率低了3%~5%（Astrup et al. 1999）。科學家們稱這種現象為適應性產熱（Adaptive Thermogenesis）、代謝適應或者新陳代謝效率增強（見圖2）。

Ultimately, research shows that people who lose weight have a 3%–5% lower resting metabolic rate than their counterparts in control groups (Astrup et al. 1999). Scientists call this process adaptive thermogenesis, metabolic adaptation or enhanced metabolic efficiency (see Figure 2).

• 向客戶傳遞體重調定點的概念

Educating Clients on Set-Point Weight

體重調定點的存在可能會使客戶覺得氣餒、沮喪。他們中大部分人可能會面對快速減重後帶來的體重的忽高忽低，這其實是很危險的。最好的方法是養成健康的生活方式，並讓他們的身體找到自己的體重調定點。

The facts on set-point weight can seem daunting or even depressing to clients who want to lose a lot of weight and keep it off. However, many of them may face graver long-term risks from rapidly losing and regaining weight repeatedly over their lifetimes. They』re probably better off focusing exclusively on a healthy lifestyle and letting the body find its set-point weight.

我們該如何讓我們的客戶重新思考「管住嘴，邁開腿」這句話呢？畢竟這句話時時刻刻都出現在他們的生活中。記住，成年人是目標導向、自我引導並遵循實際經驗的。他們傾向於學習那些最能幫助他們達成目標的生活經驗及指南。他們願意學習，並且渴望將學到的新知識運用到日常生活之中（Knowles, Holton & Swanson 2011)。

But how do we get clients to rethink the 「eat less, move more」 model they』ve been sold all their lives? Remember, adult learners are practical, goal-oriented and self-directed. They base learning on their life experience and the guidance most relevant to achieving their goals. They want to learn and are eager to integrate new knowledge into their daily lives (Knowles, Holton & Swanson 2011).

下面的一些技巧能幫助客戶更好地理解體重調定點的重要性：

Use these tips to help clients understand the importance of set-point weight:

• 探尋他們減重的動機

Explore Their Motivation for Weight Loss

是什麼在支持著你的客戶減重？是希望變得更健康？還是為了提升運動能力？要改變的是生活方式，而不是僅僅是體重指標。如果可能的話，幫助客戶重新設定動機，讓他們的動機更多的體現在健康和體重維持上，而不是減重。

What is fueling your clients』 weight loss efforts? A desire to be healthier? A need to improve function? Help people connect lifestyle change to indicators beyond weight. When possible, reframe a client』s motivation to focus on health and weight maintenance instead of weight loss.

你可以說:「我理解您迫切地想改善健康狀況。很多研究表明隨著生活方式的改變，比如飲食更健康、更多的體力活動，儘管此時體重可能只減輕了一點或者一點沒有變，但是您的健康卻得到了極大的改善。」

You could say: 「I know you are motivated to improve your health. A lot of studies show that with lifestyle changes, including better nutrition and more physical activity, health improves a lot, even with just small amounts of weight loss or just weight maintenance.」

• 用可完成的目標進行激勵

Motivate With Achievable Goals

當一位客戶希望減掉大量的體重時，多花點時間研究一下方案，並且通過SMART原則——Specific（具體的）, Measurable（可量化的）, Attainable（可實現的）, Relevant（相關的）以及Time-bound(有時限的)來設定目標。想要減重成功，一定要抵制誘惑。如果一定要設立一個要減多少重量的目標，每周目標減1~2磅（即0.45-0.9公斤）。但一定要向客戶強調，最難的部分不是減輕體重，而是維持體重。要讓客戶知道他將要面對什麼。

When a client wants to lose large amounts of weight, take the time to explore further and establish SMART goals—specific, measurable, attainable, relevant and time-bound. Avoid the temptation to fully endorse large weight loss goals. If you must establish weight loss goals, aim for 1–2 pounds per week, emphasizing that the hardest part of the change is not losing weight; it』s keeping it off. Make sure clients understand what they』re up against.

• 提供成功的案例

Provide Examples of Success

特別對於那些知道調定點機制的客戶，成功的案例能極大地激勵他們的訓練熱情。分享一些其他客戶的成功案例。當然，來源可以更廣一點，比如從美國國家體重控制註冊中心中獲得成功案例。

Success stories can motivate clients, especially those who understand how the body resists losing lots of weight. Share success stories from other clients or more broadly from places like the National Weight Control Registry.

你可以說：「這可能會有一些難度，但是很多人都成功了，並且把體重保持下來了。在美國國家體重控制註冊中心登記的大約3000名參與者，有大約87%的人都能在把體重降低10%後，把體重保持5年，更有甚者達到了10年。我們也在學習他的成功經歷。」

You could say: 「It』s challenging, but many people have successfully lost weight and kept it off. Among nearly 3,000 participants in the National Weight Control Registry, about 87% were able to maintain a 10% weight loss for 5 and even 10 years. And we are learning more and more about how some people maintain weight loss.」

• 了解客戶減重的經歷

Explore Clients』 Weight Loss Experience

向客戶詢問他們為了減肥所做過的嘗試。他們是否回到了體重調定點？與他們最開始的體重相比，他們現在體重處於什麼水平？

Ask clients about their attempts to lose weight. Did they return to a set-point weight? Where do they stand now relative to their starting weight?

你可以說：「可以講講您為了減重或者改善健康所做過的嘗試嗎？有哪些是有效的？哪些您覺得比較有難度？」

You could say: 「Please tell me a little bit about the ways you have tried to lose weight or improve your health in the past. What worked? What was challenging?」

• 找到障礙所在

Recognize Barriers

幫助客戶做好心理準備，應對長期減肥所會面對的障礙與干擾。

Help clients get mentally ready for common obstacles to long-term weight loss.

你可以說：「當人們開始減重時，儘管完全遵守著減重計劃，但是胃和大腦還是會發生一些變化，使得體重難以改變。」或者說：「當您的體重低於調定點，大腦就會讓您吃得更多，同時釋放激素來降低代謝率。如何應對這些變化呢?」比如說，客戶可以選擇吃有飽腹感、低能量和高營養的食物，如水果和蔬菜，並遠離精加工、高熱量且高糖的食物。

You could say: 「When people lose weight, changes happen in the stomach and the brain that make it challenging to keep the weight off, despite full adherence to a weight loss plan.」

Or, 「When your weight goes below your body』s 『preferred weight,』 your brain tells you to eat more while releasing hormones that tell your metabolism to slow down. How might you plan for these changes?」 For example, clients might focus on having filling, low—calorie, nutrient-dense foods like fruits and vegetables on hand and reducing access to highly processed, high-calorie, sugary foods.

• 注重健康的生活方式並且防止體重反彈

Focus on Healthy Lifestyle and Prevention of Weight Gain

即使體重沒有減輕，客戶也能變得更健康。讓客戶不要死盯著體重數字的變化，我們應當幫他們提升的是整體健康水平。

Clients can get healthier without weight loss. Help them identify steps that will improve health regardless of the effect on weight.

你可以說：「為了達成我們制定的目標，今天願意試一下哪個新動作呢？」

You could say: 「What one or two actions could you do differently, starting today, to achieve your health goals?」

客戶總是希望體重能減輕，如果只是僅僅保持體重，他們會覺得計劃沒什麼效果。但是事實上，體重的維持才是最切實可行的目標，也是最有效的結果。

Admittedly, weight maintenance goals seem less exciting to clients than weight loss goals. But unlike weight loss objectives, maintenance goals are achievable and effective.

• 對積極的改變予以鼓勵

Praise Positive Changes

鼓勵客戶做出積極的改變，比如改善營養結構和提升運動量，弱化他們對體重改變的關注度。幫他們養成習慣，鞏固這些積極的改變。

Acknowledge and affirm positive changes designed to boost health, especially those that improve nutrition and raise activity, regardless of whether weight loss happens. Help clients establish routines and habits to reinforce these improvements.

你可以說：「我們約定好了，這周您每天都會吃早餐，要遵守約定哦！」

You could say: 「This week, you planned to have breakfast every day, and you followed through with it. That shows a lot of commitment.」

• 避免指責

Avoid Blame

當客戶面臨挫折或者沒有完成他們的目標時，告訴他們這是正常的，剛開始做出改變時，我們都要先對抗自己身體的惰性。

When clients suffer setbacks or miss their goals, remind them that lapses and relapses are part of the journey, particularly when their metabolism is working against them.

如果一個客戶體重開始反彈，一定要告訴他不要沮喪，要繼續堅持生活習慣的改變。因為即使成功減了大量體重，由於體重調定點的存在，他的體重仍然有可能反彈。

If clients gain weight, you』ll have to troubleshoot for opportunities to reinforce the importance of lifestyle changes. Just remember that clients who stick to a weight loss maintenance plan after losing many pounds can still get heavier as the body tries to restore its set-point weight.

• 以人為本

Use 「People-First」 Language

「以人為本」的意思就是讓人們不要貼標籤。用「超重」這個中性詞來代替「胖子」這種帶貶義色彩的詞。相比於胖子這個充滿歧視感的稱號，用體重超重或者身體質量分數（BMI）過高會更好一點。

「People-first」 language allows people to acknowledge a disease or condition without being defined by it. That means saying people have obesity or excess weight rather than saying they are obese or overweight people. Obesity carries so much stigma that it』s often advisable to avoid the word altogether and instead talk about excess weight or increased body mass index (or BMI).

• 創造積極的運動體驗

Create Positive Exercise Experiences

一有機會就要向客戶強調體育運動對減輕和維持體重的重要作用。一旦創造出積極的運動體驗，那減重的目標也就近在咫尺了。

Never waste an opportunity to prove to your clients that physical activity is fundamental to successful weight loss maintenance. When you』re creating positive activity experiences, you』re driving home the importance of combining diet and exercise to maintain weight loss.

• 確保客戶明白了你的意思

Check for Understanding

當你給客戶介紹什麼是體重調定點時，確保他們明白你在說什麼。

When you』re educating clients about set-point weight, make sure you double back to ensure they understand what』s at stake.

你可以說：「體重降低時您的身體是怎麼應答的？這對您的減肥計劃有影響嗎？」

You could say: 「How do you think the body responds to weight loss? How will knowing this change your approach to losing weight?」

• 闢謠

Dispel Myths

對客戶和同事進行減重偽科學的闢謠。讓他們明白：想減輕體重，並不是堅持一個計劃，或者「管住嘴，邁開腿」這麼簡單。

This goes for colleagues and clients: Dispel myths or misconceptions about weight loss and weight loss maintenance. In particular, help people understand that weight loss maintenance is not as simple as 「sticking with the plan」 or embracing an 「eat less, move more」 approach.

• 慶祝成功

Celebrate Success

對於新手來說，要重視他們的進步，並慶祝他們的成功。

Make a concerted effort to celebrate accomplishments and successes, especially if they are not tied to a specific number on a scale.

• 觀念必須轉變

Minds Must be Changed

健身專業人員經常能發現：節食加上鍛煉能使客戶在6個月內快速的降低體重。但是如果不重視維持，50%的人減掉的體重會在5年內反彈，有的人反彈時間甚至會更短。（Montesi et al. 2016）

Health and fitness professionals see it all the time: Dietary restrictions and exercise help clients melt away pounds fairly quickly, with peak results occurring about 6 months out. But without ongoing weight management, 50% of people regain their lost weight within 5 years, and many do it much sooner (Montesi et al. 2016).

顯然，光靠毅力和服從還不夠，我們的體重最終還是會回歸到調定點。那應該怎麼辦呢？最好還是將注意力轉移到生活方式的改變上，設定一級一級的目標，改善營養結構並增加運動量。

We now know that willpower and compliance may not be enough to overcome the body』s natural tendency to revisit its set-point weight. Given these obstacles, fitness pros and clients might be better off focusing on lifestyle changes centering on achievable goals for nutrition and exercise.

當然在完成這個轉變之前，我們需要明白飲食、體力活動和代謝3者之間的相互作用，之後才能通俗易懂地告訴我們的客戶——什麼是身體調定點。我們得知道，較低的BMI值或者一個完美的體型並不能完全代表健康的生活方式。

Making that transition requires us to understand the interplay of diet, activity and metabolism. Furthermore, we have to translate the complexities of set-point weight into simple, direct language that clients can easily understand. And finally, we must agree that a healthy lifestyle does not require a low BMI or a picture-perfect body shape.

• 減重：我們怎麼堅持

Weight Loss: How Do We Make It Stick?

大部分的研究表明，當體重在「調定點」體重的基礎上減少了10%或者更多時，代謝適應便開始起作用，身體會嘗試著回到「調定點」體重（Muller, Endele & Bosy-Westphal 2016）。這時候，身體會希望你吃得更多而動得更少，對於減重的人來說，這將是場長期的戰鬥。

Most studies suggest that after weight loss of 10% or more of baseline body weight, metabolic adaptation kicks in and the body tries to return to its baseline weight (Muller, Endele & Bosy-Westphal 2016). Thus, people who lose substantial amounts of weight face a constant battle to counteract metabolic forces prodding them to eat more and exercise less.

而那些減輕了體重的10%以上並維持了1年以上的人，通常都有以下的共同點：

People who have succeeded in this battle—losing more than 10% of body weight for more than 1 year—tend to share similar habits:

• 膳食：他們採取少食多餐、低卡、低油的飲食控制策略（包含早餐）。
• Diet. Their daily lifestyle includes a portion-controlled, low-calorie, low-fat diet (including breakfast).
• 運動：每天至少運動1小時，每周至少稱重一次，每周看電視的時間少於10小時。
• Activity. They exercise for at least 1 hour per day, weigh themselves at least weekly and spend less than 10 hours per week watching television.

資源：美國國家體重控制登記處，nwcr.ws/research

Source: The National Weight Control Registry, nwcr.ws/research

• 體重調定點會改變嗎？

Can Set-Point Weight Be Changed?

既然體重調定點這麼重要，那麼它能被重新設定嗎？遺憾的是現在並沒有這方面的研究證據。體重調定點受基因、成長環境及其他不可知變數影響。而且計算體重調定點也不簡單。相關研究還沒有弄明白它到底確定於在我們青春期、妊娠期還是中年時期，或者它可能在我們很小的時候就被「編程」了。（Schwartz et al. 2017）

It』s only natural for fitness pros and clients to wonder if it』s possible to recalibrate set-point weight. Unfortunately, the evidence is not encouraging. Set-point weight is determined by genetics, environmental exposures and many other variables we don』t fully understand. It』s not easy to calculate set-point weight—studies have not established whether it』s determined in adolescence, pregnancy or middle age—or if it』s perhaps 「programmed」 even earlier in life (Schwartz et al. 2017).

想要調整體重調定點的可能性並不大。大部分研究也表明用飲食或行為干預來調整體重調定點也是困難的。

All these unknowns make it unclear how we might alter set-point weight, though most studies suggest that changing it through dietary or behavioral interventions is difficult.

一個有趣的現象是，在通過手術使體重減輕後，代謝適應並沒有發生。（Schwartz et al. 2017）這就意味著減脂手術後，身體的體重調定點被重新設定了。這樣看來，做手術減肥比正常運動減肥效果好。話雖如此，但還是不推薦選擇手術的方式來減重，畢竟手術主要還是針對嚴重肥胖患者所採取的特殊手段。

Interestingly, metabolic adaptation does not seem to occur after bariatric surgery (Schwartz et al. 2017), which could represent a permanent resetting of body weight. This is likely part of the reason why bariatric surgery has significantly better weight loss outcomes than those achieved through diet and exercise. While appropriate for some people with severe obesity, bariatric surgery is not a practical option for most people.

參考文獻Reference

Astrup, A., et al. 1999. Meta-analysis of resting metabolic rate in formerly obese subjects. American Journal of Clinical Nutrition, 69 (6), 1117–22.

Fothergill, E., et al. 2016. Persistent metabolic adaptation 6 years after 「The Biggest Loser」 competition. Obesity, 24 (8), 1612–19.

Knowles, M.S., Holton, E.F., & Swanson, R.A. 2011. The Adult Learner: The Definitive Classic in Adult Education and Human Resource Development (7th ed.). New York: Taylor & Francis.

Montesi, L., et al. 2016. Long-term weight loss maintenance for obesity: A multidisciplinary approach. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy, 9, 37–46.

Muller, M.J., Enderle, J., & Bosy-Westphal, A. 2016. Changes in energy expenditure with weight gain and weight loss in humans. Current Obesity Reports, 5 (4), 413–23.

Schwartz, M.W., et al. 2017. Obesity pathogenesis: An Endocrine Society scientific statement. Endocrine Reviews, 38 (4), 267–96.

Sumithran, P., et al. 2011. Long-term persistence of hormonal adaptations to weight loss. New England Journal of Medicine, 365 (17), 1597–1604.

作者：Natalie Digate Muth, MD, MPH, RDN, FAAP

翻譯：戴佳希