為何體重反彈容易，減肥卻這么困難?發表于《肥胖》(Obesity)雜志上的近期研究表明，實際上我們的身體機制抗拒體重減輕。節食時，人體的靜息代謝率降低，當我們運動量很少時，燃燒的熱量就很少。這項研究的發起人表示減肥需要“機警地與代謝適應過程作斗爭”。
The study followed 14 participants of the US version of the TV show The Biggest Loser. The researchers found that, after six years, all but one of the contestants in their study had regained weight. On average, they weighed 20st 10lb (131.5kg), compared with the average starting weight of 23st 6lb (149kg) and the 14st 4lb (91kg) at which they finished the show.
這項研究跟蹤調查了美國版的電視節目《超級減肥王》(The Biggest Loser)中的14位參與者。研究人員發現，六年后，這項研究中除一位參與者外，其他所有人的體重都反彈了。他們現在的平均體重是290磅(131.5千克)，而剛參加節目時的平均體重是328磅(149千克)，節目結束時的平均體重是200磅(91千克)。
The solution
解決方法.
Six years is a long time, and being, on average, 2st 10lb (17kg) lighter is not insignificant. But the odds were stacked against the participants. The study showed that, before the competition, the group burned a daily average of 2,600 calories at rest, but this fell to around 2,000 calories a day when it finished. Six years later, instead of creeping back up to its normal level, their resting rate had slowed further to 1,900 calories a day. On average, the resting metabolic rate was 500 calories a day less than you would expect for the age and body composition of the person. So, the contestants had to eat less to stay at their lower weight. While researchers knew that dieting reduces the resting metabolic rate to save energy, this study shows how savagely your body subverts weight loss.
六年的時間很長，平均每個人減重38磅(17kg)，其效果并不顯著。但參與者減肥成功的機會不大。研究表明，在減肥比賽開始前，這群參與者每天不活動時平均能消耗2600卡。但節目結束時，他們每天不活動時大約只能消耗2000卡了。六年后，他們的靜息代謝率進一步放緩，每天只能消耗1900卡，而沒有回升到正常水平。考慮每個人的年齡和身體組成，他們平均的靜息代謝率比期望的低500卡。所以，參與者必須減少食物攝入以保持較低體重。研究人員知道節食會降低身體的靜息代謝率以儲存能量，而這項研究表明了我們的身體機制瘋狂地抗拒體重減少。
This was a small study without controls, though, and weight loss is influenced by factors such as genetics and hormones. Other studies show that some people are less affected than others. The report on The Biggest Loser participants cites another study showing that obese people who have weight-loss surgery seem to escape this metabolic adaptation. Somehow, the body resets to a new normal weight and the resting metabolic rate doesn’t fall. For the rest of us, being vigilant about what we eat, and building up muscle mass (which is lost with age) through aerobic exercise and strength training are the only ways to fight back.
盡管這是一項沒有對照組的小型研究，但減肥會受到遺傳和激素等多種因素的影響。其他研究表明，一些人受到遺傳和激素的影響較小。有關《超級減肥王》參與者的報告引用了另一項研究。該研究表明，做過減肥手術的肥胖者似乎能夠擺脫代謝適應過程。不知為何，他們的身體能夠適應新的正常體重，靜息代謝率也不會降低。我們其余的人，必須要對自己的飲食特別上心，通過有氧鍛煉和力量訓練的方法練出肌肉群(隨著年齡增長會喪失)，這是防止體重反彈的唯一方法。
Your resting metabolic rate determines only a proportion of your energy expenditure. If you burn off more calories than you eat, you will lose weight. Other research suggests that reducing calories by 20% and doing moderate exercise for 20 minutes a day will keep weight off.
靜息代謝率只能決定你的一部分能量消耗。如果你消耗的熱量比攝入的多，你的體重就會減輕。其他研究表明，每天少攝入20%的熱量，適度鍛煉20分鐘能夠減肥。
