This proportion is significantly higher than the 1 in 10 cases currently attributed to excess weight, using body mass index (BMI), and indicates that the true impact of obesity on breast cancer risk has probably been underestimated. mother.
This finding is crucial for planning more effective prevention strategies, the researchers write.
BMI is not necessarily a very accurate measure of body fat, particularly in older women, because it does not take into account age, sex or ethnicity, the researchers write.
In the study they compared BMI with the CUN-BAE (University of Navarra Clinic – Body Adiposity Estimator), a validated measure of body fat that takes into account age and sex, in 1,033 postmenopausal white women with breast cancer and 1,143 free of the disease, but matched by age, sex, and geographic region.
All women who participated in the study were part of the multicenter case-control project (MCC)-Spainwhose objective is to investigate the environmental and genetic factors related to cancers of the intestine, breast, stomach, prostate and chronic lymphocytic leukemia in people between 20 and 85 years old.
The participants, from 12 Spanish provinces (Asturias, Barcelona, Cantabria, Girona, Granada, Guipúzcoa, Huelva, León, Madrid, Murcia, Navarra and Valencia) were asked about possible influential risk factors, including sociodemographic data, lifestyle personal and family life and medical and reproductive history.
Information about their diet was collected using a Food Consumption Frequency Questionnaire validated, composed of 140 items. A self-administered questionnaire was also used to obtain details about their habitual alcohol consumption between the ages of 30 and 40.
body fat
Regarding the evaluation of body fat, two measures were used: the CUN-BAE and the body mass index (BMI).
The CUN-BAE classifies body fat into four categories: less than 35%, 35%-39.9%, 40%-44.9%, and 45% or more. On the other hand, BMI classifies weight into the following categories: less than 25 kg/m² (normal weight), 25-29.9 (overweight), 30-34.9 (obese) and 35 or more (severe obesity).
The study found that the average BMI was 26 in the comparison group and 27 in women with breast cancer. 45% of the comparison group had a BMI < 25, and obesity occurred in 20% of that group and in more than 24% of those affected. Regarding the CUN-BAE, 20.5% of the comparison group and 16% of the women with cancer had values < 35%. A CUN-BAE ≥45% doubled the risk of cancer in postmenopausal women. It was estimated that 23% of cancer cases were attributable to excess body fat using BMI, increasing to 38% using CUN-BAE, especially in hormone receptor-positive cases.
Although the researchers point out that causal relationships cannot be established from this case-control study, they acknowledge that the CUN-BAE formula was calculated with a sample of sedentary people, and that the number of cases of breast cancer without hormone receptors positives was small.
“The results of our study highlight the need to reevaluate how we measure excess body fat, particularly in postmenopausal women. Although BMI is the classic and very predominant indicator in the clinic, perhaps it is time to renew. The CUN-BAE offers a more accurate measure of body fat using readily available information such as weight, height, age and sex. “What could allow a more precise identification of women at risk of developing breast cancer and initiate prevention strategies earlier,” says the researcher. Veronica Dávila Batista.
Dávila adds that “relying exclusively on BMI is slowing down the prevention of cancer and other diseases related to obesity. We are creating a false sense of security and normalizing being overweight. Obesity is a metabolic disorder and a chronic inflammatory state, the implications of which go far beyond excess weight. “Our goal should be to promote optimal metabolic health, rather than focusing solely on weight.”
The results of our study highlight the need to reevaluate how we measure excess body fat, particularly in postmenopausal women.
Its use in other tumors is something that is being studied. ‘Since CUN-BAE was designed to be a metabolic marker, it is possible that this finding is also relevant to other types of hormone-sensitive cancers. But it has not yet been studied. Together with Vicente Martin, of the University of Leon“This week we sent a similar manuscript for review with the CUN-BAE and colorectal cancer with very interesting results, finding differences in left and right colon cancer.”
In his opinion, “BMI does not provide an accurate assessment of body composition, especially in older women, where fat tends to redistribute and increase. “The use of new estimators, such as the CUN-BAE, would allow us to develop more effective and personalized preventive strategies to reduce the risk of cancer.”
In statements to Science Media CenterJosep Maria Borràs, scientific coordinator of the Cancer Strategy of the National Health System and director of the Catalan Oncology Plan«the study is very well designed and clearly allows us to answer the question posed. “It is interesting and provides crucial information: how we measure body fat and how it is distributed matters a lot, and not just the excess weight measured with the body mass index.”
The researcher highlights that the use of the CUN-BAE to identify women with a higher risk of breast cancer due to excess body fat would allow more specific prevention recommendations to be offered, which could theoretically reduce the incidence of breast cancer in postmenopausal women.
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