In prehistoric times, natural selection favored genotypes that could endure harsh conditions by stocking the most fat.

在史前時代，天擇留下的基因，是能靠儲存大部分脂肪生存於嚴酷條件下的。

With chronic malnutrition being the norm for most of human history, genetics evolved to favor fat storage.

由於在大部分人類史之中，長時間的營養不良是稀鬆平常的事情，基因便演化成傾向於儲存脂肪。

So when did body fat become problematic?

那又是從什麼時候開始脂肪成了問題？

The negative impacts of being overweight were not even noted in medical literature until as late as the 18th century.

過重的負面影響在 18 世紀以前一直都沒有在醫學文獻中被提到。

Then, technological advances coupled with public health measures resulted in the betterment of the quantity, quality, and variety of food.

接著，科技的發展加上公共衛生的改善帶動了食物種類的增加，以及質、量的精緻化。

Sustained abundance of good food enabled a healthier population to boom economically.

穩定且充足的食物來源確保了人口成長夠使經濟更加繁盛。

Output increased, and with it, leisure time and waistlines.

當產能提升，休息時間、和腰圍也都悄悄增加。

By the mid 19th century, being excessively overweight, or obese, was recognized as a cause of ill health, and another century later, declared deadly.

在 19 世紀中以前，超重或者肥胖被視為是不健康的結果，而在後來的時代，則被認為是致命的。

What is the distinction between being overweight and being obese?

過重跟肥胖差別在哪裡？

A calculation called the BMI breaks it down for us.

一個被稱為 BMI 的指標能替我們解答。

For example, if someone weighs 65 kilgorams and is 1.5 meters tall, they have a BMI of about 29.

例如，有一個人是 65 公斤，身高是 150 公分， 那麼他的 BMI 值就是29。

Obesity is a condition of excess body fat that occurs when a person's BMI is above 30, just over the overweight range of 25 to 29.9.

體脂肪過高是肥胖的起因，當一個人的 BMI 值超過 30 就會發生，就正好和過重在 25-29.9 的範圍銜接。

While BMI can be a helpful estimate of healthy weight, actual body fat percentage can only really be determined by also considering information like waist circumference and muscle mass.

雖然 BMI 可以評估出健康體重的範圍，但體脂肪的實際比例只能由腰圍和肌肉量此類的數據去計算。

Athletes, for instance, have a naturally higher BMI.

舉例來說，運動員自然會有較高的 BMI。

So how does a person become obese?

那麼一個人到底是怎麼樣變胖的？

At its most basic, obesity is caused by energy imbalance.

簡單來說，肥胖是由能量收支不平衡造成的。

If the energy input from calories is greater than the energy output from physical activity, the body stores the extra calories as fat.

如果食物提供的熱量比從事動態活動消耗的能量還要多， 那麼身體就會將剩餘的能量儲存為脂肪。

In most cases, this imbalance comes from a combination of circumstances and choices.

總體來說，能量的收支不平衡是由每個人不同的情況和選擇造成的。

Adults should be getting at least 2.5 hours of exercise each week, and children a whole hour per day.

就成人而言，每個禮拜至少要運動 2.5 小時，小孩則是需要每天一小時。

But globally, one in four adults and eight out of ten adolescents aren't active enough.

然而從全球的數據來看，四個成人中就有一個運動量不足，青少年則是高達十個就有八個運動不到建議時數。

Calorie-dense processed foods and growing portion sizes coupled with pervasive marketing lead to passive overeating.

高熱量的加工食品，精緻化的食物，再加上無處不在的廣告， 造成人們被動的持續不必要的飲食。

And scarce resources, and a lack of access to healthy, affordable foods creates an even greater risk in disadvantaged communities.

除此之外，天然食物來源的稀少，和無法取得健康、經濟實惠的食物，形成了不利的環境，更提高了肥胖的機率。

Yet, our genetic makeup also plays a part.

然而，我們基因的影響也是舉足輕重。

Studies on families and on separated twins have shown a clear causal hereditary relationship to weight gain.

各項關於雙胞胎的家族基因研究，查證了不同基因繼承和體重增加趨勢的關係。

Recent studies have also found a link between obesity and variations in the bacteria species that live in our digestive systems.

進來的研究也發現了肥胖和各種生存在消化道系統細菌之間的關聯。

No matter the cause, obesity is an escalating global epidemic.

無論是哪個原因，肥胖已經成為日益嚴重的全球性課題。

It substantially raises the probability of diseases, like diabetes, heart disease, stroke, high blood pressure, and cancer.

它大大的增加了患上各種疾病的機率，例如糖尿病、心臟疾病、中風、高血壓，以及癌症。

It affects virtually all ages, genders, and socioeconomic groups in both developed and developing countries.

不論年紀、性別、經濟體，在已開發、開發中國家都會被影響。

With a 60% rise in child obesity globally over just two decades, the problem is too significant to ignore.

在二十年內，肥胖兒童的比例增加了百分之六十，這個問題是不容忽視的。

Once a person is obese, the climb to recovery becomes progressively steeper.

當一個人變胖之後，減重的過程會變的困難。

Hormonal and metabolic changes reduce the body's response to overeating.

荷爾蒙和新陳代謝的變化會使人體忽略過度飲食的行為。

After losing weight, a formerly overweight person burns less calories doing the same exercises as a person who is naturally the same weight, making it much more difficult to shed the excess fat.

在減重之後，曾經過重的人，在做相同的運動時， 燃燒的脂肪會比原本就在這個體重的人少， 使他們更難減去多餘的脂肪。

And as people gain weight, damaged to signaling pathways makes it increasingly difficult for the brain to measure food intake and fat storage.

而增加體重的時候，對訊息傳輸造成的傷害，會使大腦無法準確分析食物的攝取量和脂肪的儲存量。

There is, however, some evidence that well-monitored, long-term changes in behavior can lead to improvements in obesity-related health issues.

有一些在行為上被精確觀察，且長期改變的證據，可以促進肥胖相關疾病的改善。

And weight loss from sustained lifestyle changes, or invasive treatments like bariatric surgery, can improve insulin resistance and decrease inflammation.

因生活方式改變，或像減肥手術此類方式達成的減重會抑制胰島素和減少發炎的機會。

What was once an advantage for survival is now working against us.

曾經是生存優勢的功能現在變成拖累自己的絆腳石。

As the world's population continues to slow down and get bigger, moving and consciously eating our way towards a healthier weight is essential to our overall well-being.

當全世界的人開始反思，開始有意識地以擁有健康體態為目標去選擇所食用的食物， 是全人類的福祉。

And with the epidemic affecting every country in the world for different socioeconomic reasons, obesity cannot be seen as an isolated issue.

肥胖影響世界上每個國家，為了經濟上的各種理由，肥胖絕對不能被視為個別的議題。

More global measures for prevention are essential to manage the weight of the world.

找出更多全球性的預防方法，是對控制世界體重有很大影響的。