限時飲食可以預防甚至逆轉肥胖

A 12-Hour Window for a Healthy Weight

限時飲食可以預防甚至逆轉肥胖

Scientists, like mothers, have long suspected that midnight snacking is inadvisable. But until a few years ago, there was little in the way of science behind those suspicions. Now, a new study shows that mice prevented from eating at all hours avoided obesity and metabolic problems — even if their diet was sometimes unhealthful.

長期以來，母親們都認為不宜在半夜吃零食，科學家們對此也持有相同的看法。但直到幾年前，人們也只是有此懷疑，卻沒有多少科學證據可以支持它。現在，一項在小鼠中進行的新研究顯示，即使有時候它們的飲食不夠健康，但只要不是一天到晚吃個不停，就可避免肥胖和代謝問題。

Researchers at the Salk Institute for Biological Studies in San Diego and elsewhere began experimenting with the eating patterns of laboratory mice in a previous study. On that occasion, some mice consumed high-fat food whenever they wanted; others had the same diet but could eat only during an eight-hour window. None exercised. The mice that ate at all hours soon grew chubby and unwell, with symptoms of diabetes. But the mice on the eight-hour schedule gained little weight and developed no metabolic problems. Those results were published in 2012.

在此前的一項研究中，美國圣地亞哥索爾克生物研究所(Salk Institute for Biological Studies)和其他機構的研究人員們開始對實驗室小鼠的飲食模式進行實驗。在該研究中，有一部分小鼠可以依自己的喜好，隨時食用高脂肪食物，而其他小鼠雖然也可以享用完全相同的飲食，但它們每天可以進食的時間限制在八小時。兩組小鼠都未進行任何運動。全天均可進食的小鼠很快就胖得圓滾滾的，健康也發(fā)生了問題，出現了糖尿病的癥狀。但是嚴格遵照八小時時間表進食的小鼠體重幾乎沒有增加，而且也未出現代謝問題。上述研究結果在2012年發(fā)表。

For the new study, which appeared in the journal Cell Metabolism in December, Salk scientists fed groups of adult males one of four diets: high-fat, high-fructose, high-fat and high-sucrose, and regular mouse kibble. Some of the mice in each dietary group were allowed to eat whenever they wanted throughout their waking hours; others were restricted to feeding periods of nine, 12 or 15 hours. The caloric intake for all the mice was the same.

而在去年12月發(fā)表于《細胞-代謝》(Cell Metabolism)雜志上的新研究中，索爾克生物研究所的科學家們分別以四種不同的飲食喂養(yǎng)四組成年雄性小鼠：高脂肪、高果糖、高脂肪兼高糖以及普通鼠糧。在每個飲食組中，又允許一部分小鼠在清醒狀態(tài)下的任何時候進食，其他小鼠每天的進食時間則分別限制在9、12或15小時。所有小鼠攝入的熱量卡路里數均相同。

Over the course of the 38-week experiment, some of the mice in the time-restricted groups were allowed to cheat on weekends and eat whenever they chose. A few of the eat-anytime mice were shifted to the restricted windows midway through the study.

在為期38周的實驗過程中，限時進食的小鼠中又有一部分獲準在周末“放縱一下”，隨心所欲地在任何時間進食。在研究的中途，還有幾只原本隨時可以進食的小鼠被轉移入限時進食組。

By the end, the mice eating at all hours were generally obese and metabolically ill, reproducing the results of the earlier study. But those mice that ate within a nine- or 12-hour window remained sleek and healthy, even if they cheated occasionally on weekends. What’s more, mice that were switched out of an eat-anytime schedule lost some of the weight they had gained.

在研究結束時，隨時可以進食的小鼠普遍都變得肥胖，并患上了代謝疾病，這印證了早期的研究結果。但相比之下，即使周末偶有放肆，那些平時每天只有9 或12小時可以進食的小鼠體型保持得很好，身體也很健康。更重要的是，從隨時進食組轉入限時進食組的小鼠原本增加的體重也有一定程度的減輕。

“Time-restricted eating didn’t just prevent but also reversed obesity,” says Satchidananda Panda, an associate professor at the Salk Institute who oversaw the studies. “That was exciting to see.” Mice that consumed regular kibble in fixed time periods also had less body fat than those that ate the same food whenever they chose.

“限時飲食不僅可以預防肥胖，還可以逆轉肥胖，”該研究的負責人，索爾克生物研究所的副教授薩特旦安達·潘達(Satchidananda Panda)說，“這樣的發(fā)現真令人興奮。”此外，與在一天的任何時間都可以食用鼠糧的小鼠相比，每天只能在固定時段食用相同食物的小鼠的體脂肪量也較低。

Precisely how a time-based eating pattern staved off weight gain and illness is not fully understood, but Dr. Panda and his colleagues believe that the time at which food is eaten influences a body’s internal clock. “Meal times have more effect on circadian rhythm than dark and light cycles,” Dr. Panda says. And circadian rhythm in turn affects the function of many genes in the body that are known to involve metabolism.

目前尚不完全清楚基于時間的進食模式是如何避免體重增加和疾病的，不過，潘達博士及其同事們認為，進食的時間影響了身體內部的生物鐘。潘達博士指出：“進食時間對晝夜節(jié)律的影響比光暗周期更大。”反過來，晝夜節(jié)律又可以影響體內許多已知與新陳代謝有關的基因的功能。