健康生活:睡覺或可助減肥

Laying up for a solid night's sleep might not sound like the best recipe for weight loss, but loads of research has pointed to the importance of sufficient shut-eye to losing weight. And a small new study shows that not getting enough sleep might severely cut into people's ability to lose extra fat.

想減肥就要把覺睡好，這在減肥的人看來好像不是個好方案。但是，大量研究已經指出，充足的睡眠對減肥的很嚴重。下面有一個小型研究，展示了睡眠不足可能會嚴重影響人體消去多餘脂肪的能力。

Researchers found that if dieters got a full night's rest, they more than doubled the amount of weight lost from fat reserves. So even though subjects lost about as much weight when they were sleep deprived as when they were well-rested, only about a quarter of the weight lost during the short sleep period was from fat. Tired-eyed dieters also reported feeling hungrier than they did when they had gotten enough sleep. Results of the study were published online October 4 in Annals of Internal Medicine.

研究人員發現如果節食的人晚上睡得好，減肥效果會好不止一倍。所以，儘管減肥的人在睡眠不足和睡眠充足時減掉的重量一樣多，但是在睡眠不足時，減掉的重量中，僅僅只有1/4是脂肪。睡眠不足的節食者也說，他們感覺比睡眠充足的時候要餓。這項研究的結果發佈在了10月4日的“內科年鑑”網絡上。

"Cutting back on sleep, a behavior that is ubiquitous in modern society, appears to compromise efforts to lose fat," Plamen Penev, an assistant professor of medicine at the University of Chicago and study co-author, said in a prepared statement. Study subjects lost about 55 percent more fat when they got ample sleep at night.

在Chicago大學的醫學助理教授，也是這篇研究的合著人Plamen Penev在一份事先準備好的的發言中說道：“當今社會，普遍認爲減少睡眠是減掉脂肪的一個妥協方法。”但是在我們實驗中志願者，他們在獲得充足的夜間睡眠時，脂肪多減了55%。

For the study, 10 overweight volunteers (ages 35 to 49 with a mean body-mass index of 27.4 kilograms) started a personalized diet plan that reduced calories (to an average of about 1,450 per day) but maintained a sedentary lifestyle. For two weeks, subjects reported to the lab to spend 8.5 hours a night in bed (with an average sleep time of about seven hours and 25 minutes), and during a second two-week period—either three months before or after the 8.5-hour nights—the same volunteers were allowed only 5.5 hours a night in bed (with an average sleep time of five hours and 14 minutes).

爲了這項研究，對10個肥胖志願者（年齡在35歲到49歲之間，平均體重指數是27.4千克）開展一項個體化節食計劃，可以降低熱量（平均每天降低1450卡），但要保持久坐的生活方式。有一個兩週的時間，志願者們每晚在牀上8.5小時（有效的平均睡眠時間大約是7小時25分），另一個2周的觀察期-可以在早於或晚於8.5小時測驗的3個月之前或之後-還是這些志願者，讓他們每晚在牀上5.5小時（平均有效睡眠時間是5小時14分）。

During both study sessions, the subjects lost about three kilograms each. Nearly half of that (1.4 kg) was from fat when the volunteers were sleeping long, but less than a fifth (0.6 kg) of the lost weight was from fat when they got less than six hours of sleep. The rest of the weight was fat-free body mass, which includes other components such as water or muscle, and is generally not the target of those seeking to lose weight.

在這兩個實驗中，志願者們每人一共減掉大約3公斤體重：有接近一半（1.4千克）是在長睡眠階段減掉的，僅有小於1/5（0.6千克）是在短睡眠階段減掉的。其餘減掉的重量來自去脂組織，例如包括水和肌肉，而它通常不是減肥者的目標。

Food cravings and metabolism are controlled in part by hormones, such as ghrelin, which stimulates hunger and lowers energy use. And when the study subjects were getting less than six hours of sleep a night, their ghrelin levels rose from 75 nanograms per liter to 84 ng per liter. Levels remained steady when subjects got plenty of rest. The volunteers were on the same tightly controlled low-calorie diet during both phases of the study, and the weight- and fat-loss difference between adequate sleep and too little sleep might otherwise be even more pronounced, the researchers behind the study speculated.

食慾和新陳代謝部分是由激素控制的，比如胃促生長素。它能刺激食慾、降低能量消耗。當志願者在每晚睡眠少於6小時的情況下，他們的胃促生長素水平從75納克/升，升高到84納克/升，而在睡眠充足時胃促生長素的水平則保持穩定。研究人員認爲，從另一方面看，由於志願者是處於同等嚴格的低卡飲食控制下，所以充足睡眠和缺少睡眠對體重和脂肪消耗的影響就更顯著了。

So despite any extra calories a person might burn while burning the midnight oil, losing sleep is hardly the best way to lose fat, this study suggests. "If your goal is to lose fat, skipping sleep is like poking sticks in your bicycle wheels," Penev said. "One should not ignore the way they sleep when going on a diet." Plenty of other research also suggests that getting enough sleep is also crucial for good long-term health in general.

所以，這個研究就是告訴大家，不管一個人在熬夜的時候消耗了多少熱量，減少睡眠都不是減肥的最好方法。Penev說道：“如果爲了減肥而不睡覺，就是在拖減肥的後腿”還說道“人們不應因減肥而不顧正確的睡眠習慣”，很多其他研究也表明，通常來說，保持充足的睡眠對人們長遠的健康也是很重要的。