“This means that not every woman who has been overweight for some time in her life will develop cancer at some point”. It shall also be noted that the risk of cancer was also dependent on how much the women were overweight.
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Being overweight for long periods as an adult significantly increased the incidence of all obesity-related cancers by 7 percent. “It would be interesting to replicate their findings, and extend this to obesity-related cancers in men as well as African Americans, Asians, and other populations”. All of these conditions have been shown to increase cancer risk as well.
Some 6 300 of the women were diagnosed with cancer. However, those who followed only the exercise plan lost a mere 2.4 percent of their starting weight.
Where did the story come from?
One author received grant funding from the National Institutes of Health, AHRQ, Merck, Amgen, Bristol-Myers Squibb, and AstraZeneca for research unrelated to the current study.
The study was led by Melina Arnold, of the International Agency for Research on Cancer (IARC) – the specialized cancer agency of the World Health Organization (WHO), in Lyon, France – and Prof.
The study was published in the peer-reviewed journal Public Library of Science (PLOS) on an open-access basis, meaning it is free to read online.
It is thought hormones released by fat in the body feed tumours. But diet or diet and exercise are more effective than exercise alone.
Once you get past the unpleasant and misleading headline, with its implications that overweight women are to blame for cancer by “refusing” to diet, the Mail’s report is reasonably accurate. Other cancers, such as kidneys, bowel and pancreas, were also more likely. It does not mention that observational studies such as this one can not prove that overweight causes cancer.
What did the research involve?
World Health Organisation researcher Dr Arnold, who worked with USA colleagues, analysed data on nearly 75,000 post-menopausal American women whose health was tracked for around 12 years.
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.
The women were weighed and measured several times during the study – and also provided their measurements from when they were 18, 35 and 50 years old.
What were the basic results? About two thirds of women were overweight or obese at some point during adulthood. The odds of the disease rose by
17 percent on average for every
decade a woman was overweight. In particular, every 10-year increase in adulthood overweight duration was associated with a 5 and 17 percent increase in risk of postmenopausal breast and endometrial cancer, respectively. No link was seen between time spent overweight and rectal, liver, gallbladder, pancreatic, ovarian or thyroid cancer. BMI is calculated by dividing weight in kilograms by height in metres squared.
How did the researchers interpret the results?
Study co-author Professor Hoda Anton-Culver, of the University of California, Irvine, said: “If this is true, health care teams should recognise the potential of obesity management in cancer prevention and that excess body weight in women is important to manage regardless of the age of the patient”.
Recent studies have suggested that the risk of cancer related to obesity is accelerated by time.
However, there are limitations. This means the study can not prove that overweight directly caused cancer.
These caveats aside, the study is a serious attempt to quantify the risk that overweight and obesity contribute to cancer risk. Participants were postmenopausal women 50-79 years old from 40 clinical centers across the USA, enrolled from October 1993 to December 1998.
The best way to keep to a healthy weight throughout life is to eat a healthy, balanced diet and take plenty of exercise.
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And given that once weight is put on, it is hard to lose, it may be particularly important for young women to watch their waistline.
