Time women spend overweight affects cancer risk


The longer a woman is overweight, the higher her risk of several cancers, researchers report.

Incentive to avoid excess weight

The study, which followed nearly 74,000 US women, found that the longer a woman carried excess poundage, the greater her risk of breast, endometrial, colon and kidney cancers.

"We've known for a long time that excess weight is important in cancer risk," said Susan Gapstur, vice president of epidemiology for the American Cancer Society.

The cancer society says excess weight contributes to as many as 20 percent of all cancer deaths.

"This study is interesting because it suggests that the number of years you spend being overweight also matters," said Gapstur, who was not involved in the research.

Read: Obesity May Up Death Risk in Older Women With Colon Cancer

And that, she said, should provide further incentive to avoid excess weight gain in the first place.

Currently, about 7 out of 10 adults in the United States are overweight, and more than one-third are obese, according to background notes with the study.

Duration of weight

The new findings are based on data from the Women's Health Initiative – a huge government-sponsored study that followed US women aged 50 to 79. At the outset, researchers measured the women's current weight and height, and asked them to recall their weight at ages 18, 35 and 50.

Over the next dozen years, just over 6,300 women developed a form of cancer that has been linked to obesity, such as breast, ovarian, endometrial, colon, kidney, liver or pancreatic cancer.

It turned out that the risk of developing any of those cancers rose in tandem with the number of years a woman had been overweight.

Read: Weight loss might reduce cancer risk

On average, the study found, the odds rose by 10 percent for every 10 years a woman had been obese. Similarly, they climbed by 7 percent for every decade she'd been overweight.

When the researchers took a closer look, four cancers were clearly connected to the duration of a woman's excess weight: breast, endometrial, colon and kidney. But the findings do not prove excess weight causes these cancers.

Difficult to isolate effects

The findings suggest that when it comes to curbing cancer risk, "obesity and overweight prevention is essential, at any age," said lead researcher Melina Arnold, of the International Agency for Research on Cancer, in Lyon, France.

Why is excess weight related to cancer risk? According to Arnold, it's difficult to isolate effects of obesity, per se, since it often goes hand-in-hand with lifestyle habits and medical conditions that have also been linked to cancer.

Those include smoking, lack of exercise, poor diet and type 2 diabetes, she said.

Her team did, however, account for some of those factors. And there was still a link between cancer risk and the number of years a woman spent in the overweight range.

Read: Obesity linked to two types of cancer

Beyond that, Gapstur said, a body of research supports the idea that excess weight itself influences cancer development.

The bottom line

For instance, extra body fat affects levels of "sex hormones", like oestrogen, she said. This may be one reason excess weight is connected to breast and endometrial cancers.

Plus, Gapstur said, that extra weight can help feed chronic inflammation in the body, which is thought to contribute to a range of diseases, including various cancers.

The bottom line, she said, is simple: "Try to maintain a healthy weight throughout adulthood."

Arnold agreed. "Having a healthy body weight is always beneficial – not only to prevent cancer, but also other diseases associated with [excess weight]," she said.

The study appears in the online journal PLOS Medicine.

Read more:

Symptoms of cancer

Treating cancer

Preventing cancer

We live in a world where facts and fiction get blurred
In times of uncertainty you need journalism you can trust. For 14 free days, you can have access to a world of in-depth analyses, investigative journalism, top opinions and a range of features. Journalism strengthens democracy. Invest in the future today. Thereafter you will be billed R75 per month. You can cancel anytime and if you cancel within 14 days you won't be billed. 
Subscribe to News24
Voting Booth
Zama zama crackdown: What are your thoughts on West Village residents taking the law into their own hands?
Please select an option Oops! Something went wrong, please try again later.
Authorities should bring in the army already
11% - 2107 votes
Illegal miners can't be scapegoated for all crime
50% - 9838 votes
What else did we expect without no proper policing
36% - 7161 votes
Vigilante groups are also part of the problem
4% - 725 votes
Rand - Dollar
Rand - Pound
Rand - Euro
Rand - Aus dollar
Rand - Yen
Brent Crude
Top 40
All Share
Resource 10
Industrial 25
Financial 15
All JSE data delayed by at least 15 minutes Iress logo
Editorial feedback and complaints

Contact the public editor with feedback for our journalists, complaints, queries or suggestions about articles on News24.