Women who put on a lot of weight after being diagnosed with breast cancer are 14% more likely to suffer a recurrence of the disease, a US study has revealed.
Those who had piled on 10% of their body weight after they were diagnosed with breast cancer were at risk of the disease returning, but those who gained a moderate amount of weight, 5% or less, were not at risk, researchers from the Kaiser Permanente Division of Research California concluded.
They discovered that the risk applied to both women who were heavy and those who were not overweight before being diagnosed with cancer. The researchers concluded that a normal-sized woman who gained 10% or more after breast cancer diagnosis had a 25% higher chance of dying than those whose weight remained stable.
Lead researcher Dr Bette Caan said: "Most women are not gaining a large amount of weight following breast cancer diagnosis. However, our analysis showed an association with poorer outcomes overall for those who do."
The findings were presented at the annual meeting of the American Association for Cancer Research in Orlando, Florida.
Dr Caan stressed that moderate weight gain did not affect breast cancer prognosis.
She said: "Women tend to worry about gaining weight after a breast cancer diagnosis. But it's actually only the larger weight gains that increase the risk of poor outcomes."
The study drew on data from the After Breast Cancer Pooling Project which looked at four groups of 18,336 breast cancer survivors. Large weight gain occurred in 16% of the women.