溜溜球减肥不太可能有癌症风险


  【24drs.com】同类研究中最大型、最全面的一篇研究的研究者指出,溜溜球减肥的现象,或者是故意减肥之后无意间复胖10磅(约4.5公斤)以上,与整体癌症风险或12种癌症的特定风险无关。
  
  根据美国癌症协会(ACS)研究员Victoria Stevens博士领衔的研究者指出,溜溜球减肥是一个流行的名词,技术上被称为体重循环,在许多研究中被认为与癌症风险有关,但那些研究有一些明显的限制。
  
  他们的研究在线发表于7月23日的美国流行病学期刊。
  
  美国癌症协会研究者指出,美国成年人有半数正试图减重,而大部份是复胖的,因此,如果体重循环是一个癌症风险因素,将会是一大公卫议题。
  
  Stevens博士指出,该研究团队透过「探讨比之前研究更多的癌症」而讨论这个议题,涵盖最多人口且包括男性,男性在之前的研究大部份被忽略。
  
  他们分析了始于1992年之「癌症预防研究II营养群体」的42,498名男性与53,709名女性。
  
  目前并无体重循环的定义,该研究在开始时的问卷中询问,故意减重至少10磅(约4.5公斤)后复胖的次数。
  
  这些研究对象回答体重循环情况之后,根据他们报告的循环次数分类:1- 4、5-9、10-19以及20次以上。
  
  在这96,000多人的分析世代中,在1994-2009年间有25,317人初次发生癌症。
  
  当研究者分析这些数据时,他们发现体重循环与男性的整体癌症风险无关(20次相较于0次者的风险比[HR]为0.96;95% 信赖区间[CI]为 0.83- 1.11)、女性则是:HR, 0.96;95% CI, 0.86- 1.08。
  
  分析时校正了身体质量指数(BMI)与其它共变项。根据Stevens博士等人指出,在10年前一篇发现乳癌与体重循环有关的研究(Am J Epidemiol. 2005;162:229-237)中,BMI被认为有所影响。
  
  体重循环与个别探讨的12种癌症无关:前列腺(包括低风险与侵犯型案例)、大肠、直肠、胰脏、肾脏、食道、肝脏、非何杰金氏淋巴瘤、多发性骨髓瘤、肺癌、黑色素瘤、和胃。
  
  研究者解释,这些结果认为,不论体重多少,体重循环不可能影响后续的癌症风险。
  
  这篇研究的一个主要限制是,没有办法评估是否是「复胖/减重幅度」与癌症风险有关。换句话说,是那些体重变化幅度比较剧烈—每个循环至少25磅(约11公斤) —的男性或女性的癌症风险比较大吗?
  
  Stevens博士表示,不幸的是,体重循环尚无标准定义,10磅(约4.5公斤)可能太少。如上所述,体重循环的量仅是在1990年代初期的问卷中所提出。
  
  但是,10磅(约4.5公斤)的循环并非体重循环研究的离群值,她报告指出,有些研究使用这个数量,有些使用的量更多。
  
  根据研究者表示,研究强度在于,问卷要求受访者回答「故意」减重的量,故意是很重要的一个因素,因为可能是抽菸等不健康的行为导致体重减少。有些研究显示,体重循环和癌症风险的关联无法控制意向。
  
  资料来源:http://www.24drs.com/
  
  Native link:Yo-Yo Dieting Is Unlikely to Be Cancer Risk

Yo-Yo Dieting Is Unlikely to Be Cancer Risk

By Nick Mulcahy
Medscape Medical News

The phenomenon of yo-yo dieting, or the intentional loss and then unintentional regain of 10 pounds or more, is not associated with overall cancer risk or specific risks for 12 cancers, according to investigators involved in the largest and most comprehensive study of its kind.

Yo-yo dieting, which is a popular term and is technically known as weight cycling, has been linked to cancer risk in a number of studies, but those have had notable limitations, according to the study investigators, led by Victoria Stevens, PhD, a researcher at the American Cancer Society (ACS) in Atlanta.

Their study was published online July 23 in the American Journal of Epidemiology.

The ACS investigators point out that nearly half of American adults are trying to lose weight, and most loss is regained. Therefore, if weight cycling was a cancer risk, it would be a broad public health issue.

The team addressed the issue on a grand scale by investigating "many more cancers than any previous study," having the largest population, and including men, who have mostly been neglected in research to date, Dr Stevens told Medscape Medical News.

They analyzed the 42,498 men and 53,709 women enrolled in the Cancer Prevention Study II Nutrition Cohort, which was started in 1992.

Weight cycles were defined by default; the study's baseline questionnaire asked the number of times at least 10 pounds was purposely lost but later regained.

The people who reported weight cycling were then categorized by the total number of cycles they reported: 1 to 4, 5 to 9, 10 to 19, and 20 or more.

In this 96,000-plus person analytical cohort, 25,317 first cancers occurred from 1994 to 2009.

When the investigators crunched the numbers, they found that weight cycling was not associated with overall risk for cancer in men (hazard ratio [HR] for at least 20 cycles vs no weight cycles, 0.96; 95% confidence interval [CI], 0.83 - 1.11) or women (HR, 0.96; 95% CI, 0.86 - 1.08).

The analysis was adjusted for body mass index (BMI), among other covariates. BMI might have confounded at least one study that found a link between breast cancer and weight cycling, according to Dr Stevens and colleagues, referring to a 10-year-old study (Am J Epidemiol. 2005;162:229-237).

Weight cycling was not associated with any of the 12 individual cancers investigated: prostate (both lower-risk and aggressive cases), colon, rectal, pancreatic, renal, esophageal, liver, non-Hodgkin's lymphoma, multiple myeloma, lung, melanoma, and stomach.

"These results suggest that weight cycling, independent of body weight, is unlikely to influence subsequent cancer risk," the investigators explain.

A notable limitation of this study is that there was no way to assess whether the "amplitude of gain/loss" was associated with cancer risk. In other words, are the men and women whose yo-yoing was more drastic — at least 25 pounds with each cycle — at risk for cancer?

"Unfortunately, there is no standardized definition of a weight cycle. Ten pounds may be low," said Dr Stevens. As noted above, the weight-cycle amount was dictated by a questionnaire drafted in the 1990s.

But the 10-pound cycle is not an outlier in the body of weight-cycling research, she reported: "Some studies have used this amount, whereas others have used more."

Among the study's strengths is the fact that the questionnaire asked participants about "purposely" losing weight, according to the investigators. The element of intention is important because weight loss can occur with unhealthy behaviors, such as smoking, they point out. Some of the studies that have shown a link between weight cycling and cancer risk have failed to control for intentionality.

The American Cancer Society funds the Cancer Prevention Study II Nutrition Cohort. The authors have disclosed no relevant financial relationships.

Am J Epidemiol. Published online July 23, 2015.

    
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