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A diagnosis of breast cancer can lead to serious weight gain for some women, a study has found.
Chemotherapy may be one of the factors involved, scientists believe.
Women given chemotherapy were more than twice as likely to have gained at least five kilograms within five years than those who were cancer free.
Having a non-hormone sensitive aggressive cancer was also strongly associated with putting on weight.
Lead researcher Kala Visvanathan, from the Johns Hopkins Bloomberg School of Public Health in the US, said: “Our study showed that women diagnosed with breast cancer and those who received chemotherapy to treat their breast cancer gained more weight within the first five years of diagnosis and treatment than cancer-free women.
“This study highlights the need for physicians and their patients, including those with a family history of the disease, to pay closer attention to weight gain during and after treatment.
“Longer follow-up is needed to confirm the persistence of weight gain in breast cancer survivors and understand the metabolic changes that may be occurring.”
A total of 303 breast cancer survivors and 307 cancer-free women were recruited for the study, published in the journal Cancer Epidemiology, Biomarkers and Prevention.
Overall, cancer survivors who were diagnosed with breast cancer within five years of the start of the investigation gained an average 1.7kg more than women without the disease.
Those diagnosed with non-hormone sensitive invasive cancer gained 3.3kg on average. Of the women given chemotherapy within the previous five years, 21 per cent put on at least five kilos.
Co-author Amy Gross, also from the Bloomberg School of Public Health, said: “This is of concern because weight gain of this magnitude in adults has been associated with increased future risk for chronic diseases like coronary heart disease, hypertension (high blood pressure) and type 2 diabetes.”
No significant weight gain was seen in women diagnosed more than five years earlier or treated with hormone therapy.
It is not clear why chemotherapy may be linked to weight gain in breast cancer patients. Some experts have suggested the treatment increases inflammation and disrupts metabolism. Patients receiving chemotherapy are also likely to be less physically active and may put on weight as a result.
“We’re looking at biomarkers in urine and blood in our survivors and in women who are cancer-free to look for the biochemical changes that may be related to this higher weight gain,” said Visvanathan.
A high proportion of overweight women belonged to the group of survivors with a family history of breast cancer or inherited gene mutations linked to the disease.
Use of cholesterol-lowering statin drugs among women treated with chemotherapy was also linked to weight gain.