Women who spend long periods of their lives being overweight experience a higher likelihood to develop obesity-related cancers, a new study says.
Melina Arnold of the World Health Organization's International Agency for Research on Cancer (IARC) led a team of researchers in examining the relationship between the length of time a woman spends being overweight and her risk of developing certain cancer types.
They made use of medical data collected from 73,913 postmenopausal women as part of the national study known as the Women's Health Initiative.
Among the specific factors the researchers explored were the participants' body mass index (BMI) scores, diet, hormone use, smoking and just how much physical activity they typically performed. The team also examined the women's diabetes and cancer history.
Researchers often use a person's BMI to determine whether or not he or she can be considered overweight or obese. Individuals who get a score of 25 to 30 fall within the overweight BMI range, while those who get a score of 30 or higher are already within the obese BMI range.
The data that Arnold and her colleagues analyzed was collected over a 12-year period, during which the participants were diagnosed with as many as 6,301 cancers associated with obesity.
The team found that for every decade the participants spent being overweight, their likelihood of developing weight-related cancers increased by as much as 7 percent.
The findings also showed that women's risk of developing endometrial cancer increased by as much as 17 percent, while their risk of developing breast cancer increased by as much as 5 percent.
The amount of excess weight the women carried during this period also significantly impacted their likelihood of developing certain types of cancers.
Arnold explained that the results were biologically-plausible, as the length of time a person spends being overweight or obese has been linked to an increased risk of developing insulin-resistance, hypertension and chronic inflammation. It is also associated with DNA damage and certain changes in the metabolism of hormones. All of these conditions have been shown to increase cancer risk as well.
The study also showed that the degree of being overweight over time also played a crucial role in increasing the women's cancer risk. This makes it difficult to issue a general statement regarding just how much a person's overall risk for developing cancer increases each year because of obesity or being overweight, according to Arnold.
The researchers pointed out that more studies are needed in order to find out whether the same results would be found in women who may have lost weight for a certain period but then regained it.
The findings of the International Agency for Research on Cancer study are featured in the journal PLOS Medicine.
