Yo-Yo Dieting Does Not Thwart Weight Loss Efforts or Alter Metabolism Long Term, Study Finds
研究發現，曾因減肥而體重反覆升降並不會影響代謝功能，也不會降低長期減肥的效果
ScienceDaily (Aug. 14, 2012) — Yo-yo dieting -- the repetitive loss and regain of body weight, also called weight cycling -- is prevalent in the Western world, affecting an estimated 10 percent to 40 percent of the population. The degree to which weight cycling may impact metabolism or thwart a person's ability to lose weight in the long run has been unclear -- until now.
體重反覆升降、屬於yoyo型的減肥民眾在西方十分普遍，據統計有10%-40%的人有此經驗。在過去，這種狀況是否會影響代謝功能，或使長期的減肥效果打折，仍無定論。但現在，這個問題有了答案。
A new study by researchers at Fred Hutchinson Cancer Research Center, published online in the journal Metabolism, for the first time has shown that a history of yo-yo dieting does not negatively affect metabolism or the ability to lose weight long term.
萊德‧哈金森癌症研究中心的研究員做了此項研究，將結果發佈於網路醫學期刊《代謝》。該研究首次證實因減肥而體重反覆升降的民眾，其代謝功能及長期減肥的效果不會因此受影響。
"A history of unsuccessful weight loss should not dissuade an individual from future attempts to shed pounds or diminish the role of a healthy diet and regular physical activity in successful weight management," said the study's senior author Anne McTiernan, M.D., Ph.D., a member of the Hutchinson Center's Public Health Sciences Division.
「減肥失敗的經驗不該影響個人未來的減肥心態，也不該使人對健康飲食及規律運動卻步。」Anne McTiernan如此表示。她是該研究的資深權威，也是萊德‧哈金森衛生科學部的一員。
Two-thirds of the U.S. population is currently overweight or obese and it is estimated that nearly half of American women are currently dieting to lose weight. Obesity is a known risk factor for many cancers as well as heart disease and diabetes. A relationship between body fat and the production of certain hormones and inflammatory markers is thought to contribute to increased cancer risk.
目前有三分之二的美國人過重或肥胖，且據統計近半數的美國女性採取節食來減肥。肥胖是許多疾病的源頭，比如癌症、心臟病，或糖尿病。體脂肪、特定荷爾蒙及發炎指標三者與癌症風險關係密切。
"We know there's an association between obesity, sedentary behavior and increased risk of certain cancers," McTiernan said. "The World Health Organization estimates that a quarter to a third of cancers could be prevented with maintenance of normal weight and keeping a physically active lifestyle."
「我們曉得肥胖與久坐有關，也會增加罹癌風險。」McTiernan繼續說，「世界衛生組織(WHO)統計發現，只要維持正常體重和規律運動，人們其實能避免四分之一到四分之三的癌症。」
The study was based on data from 439 overweight-to-obese, sedentary Seattle-area women, ages 50 to 75, who were randomly assigned to one of four groups: reduced-calorie diet only, exercise only (mainly brisk walking), reduced-calorie diet plus exercise and a control group that received no intervention. At the end of the yearlong study, participants on the diet-only and diet-plus-exercise arms lost an average of 10 percent of their starting weight, which was the goal of the intervention.
該研究找了439名過重至肥胖、生活在西雅圖的女性，習慣久坐，年齡介於50-75歲，隨機分入以下其中一組：減少熱量攝取組〈主要運動為快走〉、減少熱量攝取搭配運動組和沒有任何干預的對照組。此研究為期一年，結束前除了對照組外，其他受試者平均減了原本體重的10%，而這也是該研究的目標。
The analysis aimed to determine whether women with a history of moderate or severe weight cycling were at a disadvantage compared to non-weight-cyclers when it came to losing weight. Of the study participants overall, 18 percent (77 women) met the criteria for severe weight cycling (having reported losing 20 or more pounds on three or more occasions) and 24 percent (103 women) met the criteria for moderate weight cycling (having reported losing 10 or more pounds on three or more occasions).
該研究主要探討相對於體重沒有什麼變動的女性，曾因減肥而體重劇烈或一般起伏的女性在減肥時是否處於劣勢。受試者有18%〈77名女性〉符合體重劇烈起伏的條件〈反覆減重超過20磅、至少三次〉；24%〈103名女性〉達到體重一般起伏的條件〈反覆減重超過10磅、至少三次〉。
Although severe weight cyclers were, on average, nearly 20 pounds heavier than non-cyclers at the start of the study, at the end of the study the researchers found no significant differences between those who yo-yo dieted and those who didn't with regard to the ability to successfully participate in diet and/or exercise programs. The cyclers also did not differ from the non-cyclers with regard to the impact of diet or diet-plus-exercise on weight loss, percentage of body fat and lean muscle mass gained or lost. Other physiological factors such as blood pressure, insulin sensitivity, and blood concentrations of hormones such as leptin (which helps make one feel full) and adiponectin (which helps regulate glucose levels) also did not differ significantly among those whose weight fluctuated and those whose did not.
平均而言，在研究初始，體重劇烈起伏的女性比正常女性重近20磅；但研究結束時，研究人員發現兩者皆能參與所設計的飲食及運動項目，且有所成果。對於以節食或節食搭配運動來減重，兩者無所差異，在體脂肪、瘦肉增減方面亦是。其他生理狀況如血壓、胰島素敏感度和血液中荷爾蒙濃度〈例如能使人感到飽足的瘦體素，或幫助調節葡萄糖的脂聯素〉在兩種受試者身上也沒有顯著差異。
These finding may represent a first in the scientific community. "To our knowledge, no previous studies have examined the effect of prior weight cycling on the body composition, metabolic and hormonal changes induced by a comprehensive lifestyle intervention in free-living women," the authors wrote.
這些發現可能是科學上的一大先例。資深研究人員寫道：「就我們所知，以往沒有任何研究探討此種現象---曾因減肥而體重起起伏伏的女性，其代謝功能或荷爾蒙分泌是否會因此而受影響。」
The National Institutes of Health, the National Cancer Institute and the Canadian Institutes of Health funded the research. The study also included investigators at Harvard Medical School, the National Cancer Institute and the University of Washington.
此項研究由美國國家衛生研究院、美國國家癌症研究所和加拿大衛生研究院共同合作；研究人員也有來自美國哈佛醫學院、美國國家癌症研究所和美國華盛頓大學。
