寵物是掌握肥胖危機的關鍵因素嗎?－bubble50 DH Freelance 中翻英英翻中

Our pets: the key to the obesity crisis?

寵物是掌握肥胖危機的關鍵嗎?

Even animals that aren’t eating too much or exercising too little are getting fat. If we can figure out why, we may have the key to our own obesity crisis – and how to stop it.

動物即使吃的不多或運動不少，也會發胖。如果能弄清楚其中的原因，我們可能就能掌握人類肥胖危機的關鍵因素，以及知道該如何阻止它。

By Jules Montague 15 January 2019

由Jules Montague所撰 2019年1月15日

Until last year, Borris would never turn down a pork chop. He was partial to ice cream during the summer and loved a Sunday roast in the winter – including beef with Yorkshire pudding, pigs in blankets, mashed potatoes, and a selection of vegetables.

直到去年為止，Borris從不拒絕豬排。在夏天，他偏愛冰淇淋，而冬天他則喜歡周日烤肉，包括牛肉和約克郡布丁、熱狗捲、馬鈴薯泥和各種蔬菜。

Borris is a five-year-old Cavalier King Charles Spaniel. By the time his owner, Annemarie Formoy, entered him into the PDSA Pet Fit Club competition, which helps obese cats and dogs slim down, he was 28kg – almost double his recommended weight. It took two people to lift him into the car, he had arthritis in one leg and his breathing was laboured. Thanks to a tailored six-month diet and exercise regime he is now 7kg lighter and has just been crowned joint competition winner with Sadie the Labrador.

Borris是一位五歲的騎士查理士王小獵犬。當牠的主人Annemarie Formoy幫牠加入一個幫助肥胖貓狗減肥的PDSA寵物健身俱樂部大賽時，牠的體重為28公斤，幾乎是牠建議體重的兩倍。需要用到兩個人才能把他抬進車內，牠有一條腿患有關節炎，而且牠還有呼吸困難的問題。幸好通過一項量身定制的六個月飲食與運動方案，現在牠減下了7公斤，而且剛剛與一隻叫Sadie的拉布拉多一起獲得了聯合競賽冠軍。

Borris, at his heaviest, was not alone. The worldwide prevalence of pet obesity lies between 22% and 44%, and rates seem to be rising. The reasons why are fairly predictable. Owners of overweight dogs feed them more snacks and table scraps, are more likely to have their pets present as they prepare their own meals and are less likely to walk them daily. Owners of obese cats tend to use food as a reward and play with them less. If a dog owner is obese, the chances are their pet will be too (this doesn’t apply to cats).

有不少胖成像Borris這樣的寵物。全世界的寵物肥胖患病率在22％到44％之間，而且這個比例似乎一直在上升。造成這樣的原因其實是可以想見的。這些體重超標的寵物，都被牠們的主人用零食和桌上的殘渣餵養，而且在他們準備自己的飯菜時更有可能讓這些寵物也出現在餐桌上，而這些主人更是很少每天帶牠們散步。胖貓的主人可能會把食物當成獎勵，卻又少和牠們玩樂。如果狗主人本身肥胖的話，他們的寵物也很有可能會肥胖（不過這不適用於養貓的情形）。

But obesity also seems to be occurring even in some domestic and wild animals who aren’t being overfed or under-exercised. If these findings are true, something else must be driving obesity and uncovering those could help tackle our own epidemic with the condition.

但是似乎肥胖的現象也出現在一些甚至沒有被過度餵養或運動不足的家養寵物或野生動物中。如果這些發現屬實，那麼必然有其他的因素導致肥胖的產生，若能揭開這些原因，將可能有助於解決人類肥胖問題的流行。

More than 1.9 billion human adults are overweight. Of these, more than 650 million are obese – that’s about 13% of the world’s adult human population. The worldwide prevalence of obesity has nearly tripled since 1975. And childhood obesity has risen alarmingly too – an estimated 41 million children under the age of five are overweight or obese.

有超過19億的成年人類體重超重。其中，超過6.5億的人有肥胖的問題，這大約佔世界成年人口的13％。自1975年以來，全球肥胖症患病率幾乎增加了三倍。兒童肥胖現象也驚人地在上升，據估計，有4100萬名五歲以下的兒童有體重超重或肥胖的問題。

The first animal clue lies at the paw of the obesity-prone Labrador retriever. “Labradors are consistently the headline act when it comes to overweight dogs,” says Eleanor Raffan, a veterinarian and geneticist at the University of Cambridge. She and fellow researchers discovered that a genetic mutation present in around a quarter of Labradors, was associated with obesity. For each copy of the mutation – which occurred in a gene called POMC – a dog was about 2kg heavier. Most of the animals the researchers studied had one copy of the mutation, but fewer had two.

第一個動物線索就存在有肥胖傾向的拉布拉多獵犬的爪子上。劍橋大學的獸醫和遺傳學家Eleanor Raffan說:「只要談到超重的狗，拉布拉多一直是第一個出現在話題中的種類。」她和研究人員發現大約有1/4的拉布拉多犬會出現與肥胖有關的基因突變。這種突變發生在一個叫做POMC的基因當中，在各項突變基因的複製上，每隻狗大概都會多重2公斤。大多數研究人員研究的動物都存有一項複製的突變基因，但少數的動物更有出現兩項的情形。

“These are dogs always in the kitchen when owners are preparing food, sticking around looking for a tidbit even if there’s not much chance of getting one, or scavenging yucky stuff on walks,” Raffan says. “But they’re not doing that because it’s fun. They’re doing it because they’re hungry.”

Raffan說:「當主人們正在準備食物的時候，這些狗總是會出現在廚房裡，即使沒有太大機會獲得食物，牠們也會在這裡四處張望，看看有沒有美味的小東西可以吃，或者在散步時撿食一些噁心的東西。但是牠們這麼做的原因不是因為有趣。牠們這麼做是因為牠們餓了。」

That’s because POMC mutations disrupt the brain’s leptin-melanocortin pathway, which regulates food intake and energy expenditure, ultimately influencing body weight. As a result, the behaviour of these Labradors becomes very food-motivated.

這是因為POMC的突變基因破壞了大腦的瘦體素-黑皮質素路徑，該路徑能調節食物的攝入和能量的消耗，最終影響體重。結果導致這些拉布拉多犬的行為變得非常容易被食物激勵。

There’s a lesson here for humans, Raffan says. “The drive to eat is as every much of a physiological drive and dominating thought as the feeling of being thirsty.”

Raffan說人類可以從這點中得到教訓。「導致我們產生想吃東西的推力就如同生理上的推力一樣，並能主導我們產生和口渴的感覺一樣的想法。」

Genes play a role in human obesity (the average heritability lies between 40% and 75%), but obesity caused by a single gene is rare. POMC deficiency, associated with severe obesity in infancy, has been reported in fewer than 50 peopleworldwide, although there are likely thousands of undiagnosed cases. But mostly, human obesity reflects multiple genetic risk variants (each with small effects) interacting in a complex way with environmental factors.

基因在人類肥胖的問題中佔據了一定的位置（平均的遺傳率在40％至75％之間），但由單一基因所引起的肥胖卻很少見。與造成嬰兒期嚴重肥胖問題有關的POMC缺乏症，據說全世界只有不到50個案例，雖然可能有數千個未確診的病例存在。但大多數的情況之下，人類的肥胖問題卻是反映在多種遺傳風險變異上（每種都存有很小的影響），它以複雜的方式與環境因素相互作用。

The good news is that animals could help us disentangle those environmental factors, too. Factory farm animals are traditionally fattened with antibiotics that transform their gut so they need less food to gain weight. New regulations have pushed antibiotic use in UK food-producing animals to their lowest level since data were first published and the EU has banned antibiotics as growth promoters in feed.

好消息是，動物也可以幫助我們解開這些環境因素。傳統上，會對工業式養殖場的動物使用抗生素增肥並改變牠們的腸道，好讓牠們需要更少的食物來增加體重。自從數據首次發布以來，歐盟已經禁止將抗生素作為飼料中的生長促進劑，而新的法規也將英國食用動物的抗生素使用量推至最低水平。

If antibiotics fatten animals, could they be doing the same to humans? The answer to that question lies in your gut. The microbiome describes the genomes of the vast colonies of micro-organisms – bacteria, fungi, protozoa, viruses, all 100 trillion of them – living in your digestive system. This community influences your weight: germ-free mice that receive gut microbes from an obese (human) twin gain more weight and body fat than mice that receive microbes from the lean twin. An imbalance in the microbiome possibly leads to not only obesity, but irritable bowel syndrome, coeliac disease, and type 2 diabetes.

如果抗生素會使動物變胖，那麼它們是否也會對人類造成同樣的結果呢？這個問題的答案在於你的腸道。微生物基因組群是指龐大的微有機體群落的基因組，這些微有機體像是細菌、真菌、原生動物、病毒，共有100兆的數量生活在你的消化系統中。這個群體會影響你的體重：從肥胖的（人類）雙胞胎中接收腸道微生物基因組群的無菌小鼠會比從精瘦的雙胞胎中接受微生物基因組群的小鼠獲得更高的體重和體脂。微生物基因組群的不平衡可能不僅會導致肥胖，還會導致大腸激躁症、乳糜瀉和第二型糖尿病。

So what causes this sort of imbalance? There is a genetic element. But in studies of animals, high-intensity sweeteners and food additives like the emulsifiers used in many processed foods have been linked to lower gut bacterial diversity. In humans, babies given antibiotics in the first six months of life led to an increased risk of being overweight in later childhood, according to one study. Six weeks of antibiotics for a heart infection was also linked to significant weight gain.

那麼導致這種不平衡的原因是什麼呢？這和遺傳因子有關。但是在動物的研究上，高甜度甜味劑和食品添加劑，例如在許多加工食品中使用的乳化劑，它與降低腸道細菌多樣性有關。根據一項研究顯示，在人類的研究中，給予一個不到六個月大的嬰兒使用抗生素，將導致他後來在兒童時期體重超重的風險增加。一個為期六個星期治療心臟感染的抗生素使用，也與顯著的體重增加有關。

But before you throw away your life-saving antibiotics, remember these studies only show an association rather than clear cause and consequence. Certain antibiotics might even shift the balance of gut microbiota away from patterns associated with obesity. Knowing this, could we somehow modify our microbiome to tackle obesity? Work is underway to do just that, with probiotics and faecal transplantation under investigation.

但是在你扔掉能救你命的抗生素之前，請記住這些研究只是顯示出有這種聯繫，而不是顯示出確切的原因和後果。某些抗生素甚至可能改變腸道菌叢的平衡，遠離與肥胖相關的模式。在了解這一點之後，我們是否可以修改我們的微生物基因組群來解決肥胖的問題呢？目前就正在以益生菌和糞便移植來進行相關的調查工作。

Obesity isn’t just something that affects domestic animals, though. Wild animals fatten up, too, but it’s usually in relation to seasonal cycles and food availability: they’ve learned to eat when food is plentiful. But researchers have seen unexpected weight gain in yellow-bellied marmots (large grass squirrels) in Colorado’s Rocky Mountains between 1976 and 2008. Marmots are now waking up around a month earlier from their eight-month hibernation, likely because climate change has altered the time between first snow melt and first frost. These extra days mean more feeding and fattening time. In the short-term, an extra 0.3kg could improve survival chances during hibernation and reproductive success afterwards. (Sadly, marmots will ultimately pay a high price as climate change increases the frequency of summer droughts.)

然而，肥胖並不僅僅影響家畜而已。野生動物也會變胖，但這通常與季節性循環和食物供應有關：當食物豐富時牠們就會多吃一點。但研究人員卻在1976年至2008年間在科羅拉多州的落磯山脈中觀察到黃腹土撥鼠(一種大型草原松鼠)的體重異常增加的現象。可能是因為氣候變化改變了第一次融雪和第一次霜降之間的時間，造成土撥鼠現在提前一個月從一般為期八個月的冬眠期中醒來。這些多出來的日子代表著牠們能有更多的時間來養胖自己。在短期內，多增加0.3公斤能夠提高冬眠期間的生存機會和之後繁殖的成功率。（可悲的是，因為氣候變化使夏季乾旱的頻率提高，土撥鼠最終會因此付出高昂的代價。）

Other environmental factors that affect obesity in animals – and perhaps humans – include sleep debt and light pollution. Mice exposed to constant light have higher body mass indices (BMIs) and glucose levels than those exposed to normal light/dark cycles.

其他影響動物肥胖(可能也包含人類)的環境因素包括睡眠負債和光害。一直暴露在光線之下的小鼠會比暴露在正常的光/暗循環光線之下的小鼠有更高的身體質量指數（BMI）和葡萄糖水平。

Oestrogen-disrupting chemicals like bisphenol-A (BPA) – found in food cans, some hard plastics, and certain types of thermal paper used for receipts and tickets – are another potential culprit. Chemical manufacturers have challenged these links and the US Food and Drug Administration currently supports its safety, but the European Food Safety Authority is currently re-evaluating the toxicity of BPA and, in January 2011, the European Commission prohibited BPA for the manufacture of polycarbonate infant feeding bottles.

破壞雌激素的化學物質，例如，存在於食品罐頭、一些硬塑料以及做成收據和門票之類的熱感紙中的雙酚A（BPA）則是另一個潛在的罪魁禍首。化學品製造商對於這種的關聯性有所質疑，而目前美國食品藥物管理局對於它的安全性也採正面的看法，但是目前歐洲食品安全局正在重新評估雙酚A的毒性，並且歐盟執委會在2011年1月禁止雙酚A用於製造聚碳酸酯嬰兒奶瓶。

A note of caution is needed, though. Focusing on these non-food related factors can distract from the undeniable impact of supersized processed meals. The truth is we’re up against external influences that are hard to resist: ingredients designed to tap into our reward pathways, large portion sizes, and the commercial normalisation of routine sugar consumption, high fat snacks and sweetened drinks.

但需要注意的一點是，關注在這些與食物無關的因素上，可能會使我們輕忽了特大號加工食品對肥胖產生無可否認的影響力。事實是我們正在面對一些難以抵抗的外部影響力：那些被當成滿足腦中獎賞路徑的成分，都體現在大份量的食物、商業標準化我們的日常糖份攝取、高熱量的零食和加糖飲料之中。

All this is coated by manipulative marketing and conflicted interests. Studies from obesity researchers with food industry ties were five times more likely to find no association between sugar-sweetened drinks and weight gain than studies whose authors reported no financial conflict of interest. One high profile researcher who argued against calorie listings by New York City restaurants had financial ties to Coca-Cola, PepsiCo, McDonald's, and Mars.

這一切都被市場操控和利益衝突所掩蓋。研究肥胖議題而與食品行業有關的研究人員，在關於含糖飲料與體重增加的研究上，會說這兩者沒有關係的可能性高於那些沒有經濟利益衝突的研究人員五倍。有一個備受矚目的研究人員反對紐約市的餐廳列出來的卡路里列表，被發現他與可口可樂、百事可樂、麥當勞和瑪氏食品都有財務上的關係。

Animals are equally susceptible to the irresistible draw of processed food – city-dwelling tamarins in Medellín, Colombia, are fatter than their rural counterparts. Although more sedentary with easier access to fruiting trees, they also gorge on biscuits and marshmallows provided by locals. One Thailand macaque made international headlines recently when he became critically unwell through overfeeding by tourists.

動物同樣無法抗拒的也容易受到加工食品的影響，哥倫比亞麥德林中生活在城市中的狨比牠們住在農村的同類還要胖。儘管更常久坐不動，也更靠近果樹，但是牠們還是會吃當地人提供的餅乾和棉花糖。最近一隻泰國獼猴由於遊客的過度餵食，使牠變得極度的不健康，也因此成為國際頭條新聞。

If animals can teach us about the causes of obesity, they might also help us understand its treatment and prevention. And research in companion animals could hold greater relevance for humans since lab rats often do not share our genetic diversity, psychosocial stressors or environment. Raffan’s Labrador study highlighted the greater similarities between canine and human POMC, compared to the rat model we traditionally study. Crucially, though, animals deserve to be helped and healed in their own right – obese pets face osteoarthritis, cancer, cardiac and respiratory problems, reproductive disorders, urinary diseases, diabetes, and pancreatitis.

如果動物能告訴我們造成肥胖的原因，它們也能幫助我們了解肥胖的治療和預防。對伴生動物的研究可能會與人類產生更大的關連性，因為實驗小鼠一般不和我們擁有相同的遺傳多樣性、社會心理壓力或環境。與我們傳統研究中的大鼠模型相比，Raffan的拉布拉多研究更加說明了在犬類與人類之間的POMC更為相似。然而，要緊的是，動物應該有權利得到幫助和治療，這些肥胖的寵物面臨的疾病有:骨關節炎、癌症、心臟的和呼吸系統的疾病、生殖障礙、泌尿疾病、糖尿病和胰臟炎。

Overweight dogs also face reduced life expectancy – their lifespan is up to two and a half years shorter compared to dogs with a healthy body weight.

過重的狗也會面臨平均壽命的縮短，它們的壽命比有著健康體重的狗還要短上兩年半。

For animals, the solutions sound familiar: regular exercise and a balanced food regimen. Specialist diets improve satiety so that dogs feel fuller for longer. Raffan suggests that highly food-motivated dogs can benefit from less in the bowl and more (or all) from puzzle feeders that allow them to indulge their food obsession in a non-fattening way while keeping them mentally and physically active.

對於動物的解決方案，我們聽起來會感到很熟悉：規律運動和均衡飲食。特殊飲食能增加飽足感，讓狗感覺飽足的時間更長。Raffan認為，非常容易被食物激勵的狗可以從減少碗中的食物並增加(或全部改成）益智餵食器的食物，讓牠們以一種不會肥胖的方式放縱牠們對食物的執念，同時保持牠們精神上和生理上的活耀。

But her key message is that we shouldn’t view obesity as some sort of moral failing in either owners or their pets.

但更關鍵的訊息是，我們不應該將肥胖視為主人或寵物某種道德上的失敗。

“We’re so used to condemning humans who are overweight as being just greedy and weak-willed,” she says. But, she points out, this is inaccurate: eating behaviour is susceptible to genetic drives – and dogs are an example of this. “Dogs don’t make value judgments. They eat because they’re hungry and this variability in dogs is hardwired.”

她說：「我們太習慣於譴責那些過重的人，認為肥胖只是與貪心和意志薄弱有關。」但是，她指出，這是不正確的觀念：飲食行為容易受到基因的驅使，狗就是其中的一個例子。「狗不會做出價值的判斷。牠們吃東西是因為牠們餓了，狗的這種變化是無法改變的。」

Experts writing in the journal Veterinary Record also caution against condemning owners without helping them or addressing underlying social problems. Although a pet’s forcible removal might be necessary if they are severely threatened, they acknowledge, “it cannot be a general solution to the widespread problem of canine and feline obesity”. They believe that many owners don’t intentionally overfeed their pets, as reflected by their tendency to underestimate their pets’ weight (it was a vet who told Formoy that her dog was in trouble. “Borris looked a bit big but you just try make excuses in your head,” Formoy says.) Similarly, few parents of overweight children recognise their child as overweight.

期刊《獸醫誌》的專家也提醒說，不要在沒有幫助牠們或沒有解決潛在社會問題的情形之下就譴責這些主人。不過，若牠們的健康受到嚴重的威脅，那麼寵物就有必要進行強制減肥，但他們承認:「這無法成為解決普遍犬貓肥胖問題的方法。」他們相信許多主人不會故意過度餵食他們的寵物，這反映在他們常會低估寵物的體重這點可以得知（Formoy說有一個獸醫告訴她說她的狗有麻煩了:「Borris的體型看起來有點大，但你卻只是在腦中找些藉口而忽略它。」）同樣地，很少有過重孩子的父母親會意識到他們的孩子過重了。

Socioeconomic status also influences obesity in both humans and animals, partly linked to neighbourhoods with less open green spaces and fewer fitness resources. Regardless of whether you’re talking about a pet or a person, obesity is a societal health issue, not a moral one – and needs wider policy changes to be addressed.

社會經濟地位也影響人類和動物的肥胖，一部分與擁有較少的綠色空間和健身資源的社區有關。無論是在討論寵物還是人，肥胖都是一個社會健康問題，而不是一個道德問題，而且還需要更廣泛的政策變化來解決它。

As for Borris, Formoy says that his competition win was bittersweet. Her father had been unwell when she signed Borris up. “He was my dad’s best mate and the competition encouraged my dad to go out on his mobility scooter with Borris by his side,” she says. Her father passed away in July. “I thought in my head, ‘Dad, me and Borris are still going to win this for you.’”

至於Borris，Formoy說牠比賽的勝利是苦樂參半的。當她為Borris報名時，她爸爸的身體並不太好。她說:「牠是我爸爸最好的伙伴，這個比賽鼓勵了我爸爸騎著他的電動代步車，讓Borris跟在他旁邊一起出門。」她的爸爸在七月時過世。「我在心裡想著:『爸爸，我和Borris仍然會為你贏得比賽。』。」

She and Borris have kept that promise. Today, Borris is busy chasing Charlie Cat around the house, his own arthritis and breathing difficulties relegated to the past. In his story of obesity conquered, Borris has a few lessons for us all.

而她和Borris確實也都遵守了這個承諾。今天，Borris忙著在房子周圍追逐Charlie Cat，牠的關節炎和呼吸困難的問題降到了過去的水平。在牠征服肥胖的故事中，Borris為我們所有人提供了一些教訓。