The odds of a woman in Canada to one day develop breast cancer are one in nine. More than half the women who have this type of cancer have no identifiable risk factor, other than their gender and advancing age. Most risk factors are not modifiable. However, there is increasing evidence that there is a link between our lifestyle and the onset of breast cancer, among other types of cancer.
According to data from the Nurses’ Health Study, which followed over 87,000 women over a span of 26 years, women who gain weight shortly before or after menopause may increase their risk of breast cancer. Conversely, losing weight after menopause may decrease their risk.
The study found that women who gained at least 25 kilos (55 pounds) since the age of 18 had almost one and a half times the risk of getting cancer than those who maintained their weight during their adult years. A gain of 10 kilos (22 pounds) after menopause could increase the risk getting breast cancer by 18%. Losing 10 kilos after menopause could decrease the risk by 57%.
Overall, the researchers estimate that 15% of breast cancer cases in the population studied may be attributable to a weight gain of at least 2 kg (4.4 pounds) since the age of 18 years and that 4.4% of cancer cases may be attributable to a weight gain of at least 2 kg since menopause. If we exclude those who used postmenopausal hormones, about 24% of cases among participants were attributable to a weight gain since the age of 18 while 7.6% of the cases were due to a weight gain since menopause.
Most breast cancers are caused by estrogens, female hormones produced mainly by the ovaries. The researchers hypothesize that adipose tissue (i.e. containing fat) becomes the primary source of estrogen after menopause. With higher levels of hormones circulating in the blood, cells in the breasts are more stimulated and are more likely to become cancerous.
The scientific community is assessing the impact our lifestyle has on our potential risk of getting cancer. When it comes to breast cancer, it is suspected that the appearance of cancerous cells may be due to alcohol and fatty food consumption, obesity, lack of physical exercise, smoking, the use of oral contraceptives and exposure to certain pesticides. The role these factors play is yet to be defined. However, they are factors over which women have a certain degree of control. Adopting a healthy lifestyle is increasingly promoted as a way to stay healthy for as long as possible. The results of this study could provide yet another reason to lose those little love handles.