A study has found that the longer a woman has been overweight or obese during her adult life, the higher her risk is of developing cancer.
Excess body fat is a leading risk factor for many health conditions. Cancer is recognised as being strongly linked to overweight and obesity with at least nine different cancers on this list.
Questions remain, however, about what particular aspects of overweight and obesity could be most important in determining cancer risk. Questions of how many years a person has been obese for in their life, and the degree of overweight, are two that are being investigated.
The association between body fatness and cancer was investigated in a study population of over 73,000 US women (aged between 50 and 79 at the beginning of the study) over a 12 year period. Around two-thirds of the women in the study had been overweight or obese at some point during their adult lives. The health of these women was then compared to those who had never been overweight or obese.
The key finding was that being overweight during adulthood was significantly associated with the risk of cancer by seven percent for every decade that the weight was carried.
For postmenopausal breast cancer, the risk elevation was five percent and for endometrial cancer, seven percent. These numbers became even higher when the degree of overweight of obesity was taken into account.
Adjustments were made for other factors related to obesity, such as physical activity, diet, smoking, hormone use and diabetes history.
Overweight can mean greater degrees of insulin resistance, chronic inflammation, DNA damage and changes in hormone metabolism. All of these are mechanisms that play a role in cancer development.
A downside of the study was its reliance on body mass index (BMI) as a sole measure of overweight and obesity, with much of this information needing to be collected retrospectively or recalled by the study participants.
When it comes to the risk of developing cancer, the finding of this study points to the importance of preventing excess weight and obesity at any age.