溜溜球減肥不太可能有癌症風險


  【24drs.com】同類研究中最大型、最全面的一篇研究的研究者指出,溜溜球減肥的現象,或者是故意減肥之後無意間復胖10磅(約4.5公斤)以上,與整體癌症風險或12種癌症的特定風險無關。
  
  根據美國癌症協會(ACS)研究員Victoria Stevens博士領銜的研究者指出,溜溜球減肥是一個流行的名詞,技術上被稱為體重循環,在許多研究中被認為與癌症風險有關,但那些研究有一些明顯的限制。
  
  他們的研究線上發表於7月23日的美國流行病學期刊。
  
  美國癌症協會研究者指出,美國成年人有半數正試圖減重,而大部份是復胖的,因此,如果體重循環是一個癌症風險因素,將會是一大公衛議題。
  
  Stevens博士指出,該研究團隊透過「探討比之前研究更多的癌症」而討論這個議題,涵蓋最多人口且包括男性,男性在之前的研究大部份被忽略。
  
  他們分析了始於1992年之「癌症預防研究II營養群體」的42,498名男性與53,709名女性。
  
  目前並無體重循環的定義,該研究在開始時的問卷中詢問,故意減重至少10磅(約4.5公斤)後復胖的次數。
  
  這些研究對象回答體重循環情況之後,根據他們報告的循環次數分類:1- 4、5-9、10-19以及20次以上。
  
  在這96,000多人的分析世代中,在1994-2009年間有25,317人初次發生癌症。
  
  當研究者分析這些數據時,他們發現體重循環與男性的整體癌症風險無關(20次相較於0次者的風險比[HR]為0.96;95% 信賴區間[CI]為 0.83- 1.11)、女性則是:HR, 0.96;95% CI, 0.86- 1.08。
  
  分析時校正了身體質量指數(BMI)與其他共變項。根據Stevens博士等人指出,在10年前一篇發現乳癌與體重循環有關的研究(Am J Epidemiol. 2005;162:229-237)中,BMI被認為有所影響。
  
  體重循環與個別探討的12種癌症無關:前列腺(包括低風險與侵犯型案例)、大腸、直腸、胰臟、腎臟、食道、肝臟、非何杰金氏淋巴瘤、多發性骨髓瘤、肺癌、黑色素瘤、和胃。
  
  研究者解釋,這些結果認為,不論體重多少,體重循環不可能影響後續的癌症風險。
  
  這篇研究的一個主要限制是,沒有辦法評估是否是「復胖/減重幅度」與癌症風險有關。換句話說,是那些體重變化幅度比較劇烈—每個循環至少25磅(約11公斤) —的男性或女性的癌症風險比較大嗎?
  
  Stevens博士表示,不幸的是,體重循環尚無標準定義,10磅(約4.5公斤)可能太少。如上所述,體重循環的量僅是在1990年代初期的問卷中所提出。
  
  但是,10磅(約4.5公斤)的循環並非體重循環研究的離群值,她報告指出,有些研究使用這個數量,有些使用的量更多。
  
  根據研究者表示,研究強度在於,問卷要求受訪者回答「故意」減重的量,故意是很重要的一個因素,因為可能是抽菸等不健康的行為導致體重減少。有些研究顯示,體重循環和癌症風險的關聯無法控制意向。
  
  資料來源: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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