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肥胖问题:如何解除人与动物的发胖危机

更新时间:2019/2/4 11:31:00 来源:纽约时报中文网 作者:佚名

Our pets: the key to the obesity crisis?
肥胖问题:如何解除人与动物的发胖危机

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,鲍里斯(Borris)才拒绝吃猪排。他喜欢夏天吃冰激凌,冬天在星期日吃烤肉,包括牛肉和约克郡布丁、猪肉饼、土豆泥以及各种蔬菜。鲍里斯是一只5岁的骑士查理王猎犬(Cavalier King Charles Spaniel)。

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.

他的主人福尔莫伊(Annemarie Formoy)把他送到动物之家宠物减肥健身俱乐部(PDSA Pet Fit Club)参赛时,他已经28公斤重了,是正常体重的两倍。他一条腿有关节炎,而且呼吸困难,要两个人一起才能把他抬上车。经过6个月的节食治疗及锻炼,他轻了7公斤,和名为萨迪(Sadie)的拉布拉多犬获得了减肥赛的并列第一名。

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).

肥胖的鲍里斯并不是个案。世界统计宠物肥胖率在22%到44%之间,而这个比率还在上升。原因大多是,这些超重狗的主人会给他们喂很多零食和餐桌上的残羹剩饭,在准备自己的餐食时也会让狗待在旁边,而且每天很少遛狗。超重猫的主人往往把食物当作奖励,很少陪猫玩耍。如果宠物的主人肥胖,养的宠物也有可能肥胖(这并不适用于猫)。

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.

但有些肥胖的家养动物和野生动物并没有饮食过量、也不缺乏运动。如果这个发现是事实,那么导致肥胖肯定还有其他因素,发现这些因素,能帮助我们解决肥胖普遍的问题。

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.

据世界范围内统计,超重的成年人超过19亿,其中有6.5亿人过度肥胖,约占世界成年人口的13%。与1975年相比,肥胖患病率增加了近二倍。儿童肥胖也在增多,据估计,5岁以下儿童中,约有4100万超重或过度肥胖。

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.

从动物身上找到的第一条线索是,肥胖的拉布拉多寻回犬的爪子。剑桥大学兽医及遗传学家拉芬(Eleanor Raffan)说:“对于肥胖的狗来说,拉布拉多一直排名首位。”她和其他研究人员发现,约有四分之一的拉布拉多狗带有与肥胖相关的基因变异。这种变异发生在名为POMC的基因中,一条狗每发生一次变异,就会增重约2公斤。大多数动物带有一个基因突变,但有少数动物带有两个突变。

“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.”

拉芬说:“这些狗在主人准备食物的时候,经常待在厨房里,即使没有得到一口吃的也会四处转悠寻找能吃的,或者在外出时捡食一些令人作呕的东西吃。他们这么做并不是因为好玩,而是因为饥饿。”

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. 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.”

这是因为POMC突变,扰乱了大脑内管理食物摄入和能量消耗的瘦素——黑皮质素通道(leptin-melanocortin pathway),改变了食物摄入和能量消耗,最终影响体重。因此,拉布拉多犬变得一切行动受食物驱动。拉芬说,人类也是相同的道理。“想吃东西的欲望和口渴的感觉一样,生理需求主导我们的想法。”

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 people worldwide, 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.

基因在人类肥胖中扮演着重要角色(平均遗传率在40%和75%之间),但由单一基因导致的肥胖是很罕见的。婴儿时期的过度肥胖与POMC缺乏症有关,全球已知有近50人患病,可能还有几千未确诊病例。大多数情况下,人类过度肥胖反映出多种基因变异(单一种影响范围很小)与环境因素以一种复杂的方式相互作用。

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,动物可以帮助我们了解环境因素的影响。饲养场通常用抗生素改变动物的肠道,让他们少吃食物多增加体重。英国新法规把食用动物抗生素的用量,降至公布以来的最低水平,欧盟已禁止在饲料中加入抗生素作为生长添加剂。

If antibiotics fatten animals, could they be doing the same to humans?

如果抗生素能让动物发胖,人类会不会受到同样的影响?

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.

人类的肠道能回答这个问题。在人类的消化系统中存在着大量的微生物菌群,上百万亿的细菌、真菌、原生动物、病毒,它们会影响人的体重。分别给予两组老鼠肥胖人和纤瘦人的肠道微生物,它们之前体内并没有此类微生物,接受了肥胖人体内微生物的老鼠体重增加了,脂肪含量高了。微生物菌群失衡不仅能导致肥胖,还能导致肠易激综合症、腹腔疾病和2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.

那是什么导致了这种失衡?有遗传基因的原因,但对动物的研究显示,高浓度甜味剂和食品添加剂,如食品加工中使用乳化剂,都会导致肠道菌群多样性降低。一项研究表明,在出生后的前6个月使用过抗生素的婴儿,儿童期过度肥胖的风险会增加。因心脏感染使用过6周抗生素治疗的也与体重增加有显著关系。

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.

但别急着扔掉这些救命的抗生素,要记住,研究只显示了两者的相关性,并没有显示明确的因果关系。某一类抗生素甚至能改变肠道微生物菌群,让其远离肥胖。了解了这些,我们能否通过改变微生物菌群,应对肥胖?相应研究正在进行中,包括益生菌和粪便的研究。

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.)

肥胖不仅只有家畜,野生动物也会发胖。野生动物会在食物充足时多进食,所以肥胖与季节变化和食物充足有关。研究人员还意外地发现,1976年至2008年间,科罗拉多州落基山脉(Rocky Mountains)黄腹土拨鼠(大型草原松鼠)的体重增加了。因气候变化改变了第一次结霜和融雪的时间,以往冬眠8个月,现在土拨鼠会提前一个月左右醒来,这些额外的日子,土拨鼠需要吃更多食物、增肥时间更长。短期而言,增重0.3公斤可以提高冬眠期的存活机会,提升繁殖成功率。让人难过的是,因气候变化会使夏天干旱多发,土拨鼠最终将付出高昂的代价。

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.

影响动物和人类肥胖的还有环境因素,包括缺乏睡眠和光污染。长期暴露在光照下的小鼠体重指数(BMI)和血糖水平,高于处在正常光照、正常黑暗周期的小鼠。

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.

破坏雌激素的化学物质双酚A(BPA),也是一个潜在的罪魁祸首。这类化学物质存在于罐头食品、硬塑料和用于打印票据的热敏纸中。化学生产商对这些联系提出了质疑,美国食品药品监督管理局目前也认可其安全性。但欧洲食品安全局正在重新评估双酚A的毒性。2011年1月,欧盟委员会禁止在制造聚碳酸酯婴儿奶瓶时添加双酚A。

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.

需要注意的是,关注这些与食物无关的因素,会让我们忽视食用过度加工食品的影响。实际上,我们面对着难以拒绝的多种外部因素,如:适合我们口感设计的食品配料,超大份量餐点,日常糖摄入量、高脂肪零食和加糖饮料。

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.

但这些很容易被操纵性营销和利益关系所掩盖。如果研究肥胖原因的人员与食品行业有关联,那么他与没有关联的研究人员相比,其报告含糖饮料与体重增加之间没有因果关系的可能性要高出5倍。一位广受关注的研究员反对在纽约市餐馆菜单上标出卡路里含量,他被认为与可口可乐公司、百事可乐公司、麦当劳以及玛氏食品有利益关联。

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.

动物同样难以抗拒加工食品的诱惑,居住在哥伦比亚麦德林(Medellín)市区的卷毛猴就比乡村的同类胖。除了久坐不动,更容易采摘果树果实之外,他们还会食用当地人提供的饼干和棉花糖。近日,一只泰国猕猴因游客过度喂食造成身体严重不适,登上了国际头条新闻。

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.

如果研究动物能找出人类肥胖的原因,那他们也可以帮我们了解如何治疗和预防肥胖。研究陪伴人类的动物比研究实验室的小白鼠对人类有更大的意义。实验鼠不具有人类基因的多样性,社会心理压力、生活环境和人类没有共同点。拉芬在拉布拉多犬的研究中特别指出,与传统小白鼠研究模式相比,犬类和人类的基因更为相似。重要的是,动物们也应得到帮助,有治愈恢复健康的权利,过度肥胖的宠物可能会患上骨关节炎、癌症、心脏和呼吸系统疾病、生殖障碍、泌尿系统疾病、糖尿病以及胰腺炎。

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

超重的狗与体重正常的狗相比,预期寿命会减少大约两年半。解决动物过度肥胖的方法很简单:定期锻炼和均衡的饮食。专业设计的饮食可以提高饱腹感,让狗感觉更饱。拉芬建议,以食物为动力的狗,可以从减少碗里的食物中获益,从益智喂食器中获得更多或所有好处,益智喂食者让狗以一种不发胖的方式享受美食,同时保持身心活跃。另一个问题是,我们不应将肥胖看做宠物或者宠物主人的道德缺失。“我们习惯谴责超重的人贪婪、没有意志力。”她说:“这并不准确,饮食习惯是受基因影响的,狗就是一个例子。狗并不能做出价值判断。他们吃东西是因为饿,这种行为习惯是与生俱来的。”

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.

在《兽医记录》(Veterinary Record)期刊中发表评论的专家指出,只谴责宠物主人,不去帮助他们、不去解决潜在的社会问题是不对的。他们认为,如果宠物身体受到了严重的威胁,采取强制措施是必要的,但“对于猫狗过度肥胖这种普遍性问题而言,这不是好的解决方案”。许多宠物的主人并不是故意过度喂食,只是低估了自己宠物的体重。(一名兽医告诉福尔莫伊她的狗生病了。)福尔莫伊回答说:“鲍里斯看起来有点壮”,这只是感觉上的错误,就好比超重儿童的家长不会意识到自己小孩超重一样。

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.

人类与动物的肥胖还受社会经济环境的影响,社区缺乏绿地和健身设施都与此有关。无论是讨论人还是宠物,过度肥胖是一个社会性健康问题,并非道德问题,这需要大力度的政策支持来解决。

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.’”

至于鲍里斯,福尔莫伊说:“鲍里斯赢了比赛,但这件事让人喜忧参半。因为在为鲍里斯报名时,我父亲的身体就已经不好,七月就去世了。我当时想,‘爸爸,我和鲍里斯会为你赢得这场比赛的。’鲍里斯是父亲最好的朋友,这次比赛也鼓励了我父亲骑着电动车去外面走走,鲍里斯跟在身边。”

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.

他和鲍里斯信守了这个承诺。目前,鲍里斯正在家里四处追赶一只叫查理(Charlie)的猫,关节炎和呼吸困难已是过去的事了。在鲍里斯战胜肥胖的故事中,为我们大家上了一课。

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