Results of a
recent umbrella review published online in BMJ have provided strong evidence to
support the association between excess body weight and 11 cancers that include G.I
tract, endometrial and postmenopausal breast malignancies.
“The
association is now clear; it’s time to get serious about prevention, “write Professors
Yikyung Park and Graham A Colditz in an accompanying editorial.
An Umbrella
review is the reviews of existing systematic reviews and only considers the
highest level of evidence to be included, namely systematic reviews and meta-analysis.[1]
Hence, the findings from this umbrella review is the strongest evidence put
forth so far linking obesity and cancer.
The study by
Kyrgiou et al. initially selected 204 individual meta-analyses from 49 papers and
further narrowed it down to 95 meta-analysis based on validity and association
provided by the studies. 76% of the meta-analyses provided varied level of
evidence for association between obesity and cancer.
The
literature search was performed for meta-analysis and reviews that investigated
association between adiposity indices and risk of developing or dying from any
cancer. Adiposity indices included in the study were body mass index, waist
circumference, hip circumference, waist to hip ratio, weight, weight gain, and
weight loss from bariatric surgery. Obesity
was defined as a body mass index (BMI) >30 kg/m2.
The nine obesity
related cancers with strong evidence were endometrial cancer (premenopausal
women), breast cancer (postmenopausal), kidney cancer, multiple myeloma, esophageal
adenocarcinoma, colon and rectal cancer (in men), biliary tract system and pancreatic
cancer. The risk of ovarian and stomach cancer increases as the weight
increases with maximum risk in obese vs. normal weight individuals.
The BMI was
measured as a continuous variable.
With every 5
units increase in BMI, the risk of developing rectal cancer increased by 9% in
men and that of developing biliary tract cancers increased by 56%.
For each 5
kg of weight gain in adulthood the risk of postmenopausal breast cancer
increased by 11% even if the women have never used HRT, similarly for .1
increases in waist to hip ratio the risk of endometrial cancer increased by 21%.
Obesity has become
a major public health problem in last four decades with the incidence being
doubled among women and tripled among men. And preventing adult weight gain can
bring down the risk of these cancers.
The authors
also stressed the importance of primary care physicians in medical practice
because they are the primary point of contact with the patients. They said “Given
the critical role of healthcare providers in obesity screening and prevention,
clinicians, particularly those in primary care, can be a powerful force to
lower the burden of obesity related cancers, as well as the many other chronic
diseases linked to obesity such as diabetes, heart disease, and stroke.”
Although
more prospective studies are needed to confirm the association, personalized
primary preventive strategies could be designed in subjects at ‘ high risk’ for
cancers.
Link to full article here.
Link to Editorial here
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