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Excess body weight is responsible for about 11% of cancers in women and 5% of men. Did you know that the risk for postmenopausal breast cancer is 1.5 times higher in overweight women and 2 times higher in women with obesity? Let’s understand more about how obesity contributes to breast cancer risk.
Being overweight or obese increases the risk for breast cancer, especially in postmenopausal women. Your Body Mass Index (BMI) determines if you have a healthy weight, are overweight, or are obese.
A BMI between 18 and 24.9 is considered healthy. A BMI between 25 and 29.9 means that you are overweight. If your BMI is higher than 30, it could indicate obesity.
Women with a BMI over 25 are at an increased risk of developing breast cancer than those with a healthy weight. In addition, this risk is exceptionally high after menopause. Being overweight or obese also increases the risk of breast cancer recurrence.
The exact link between increased weight and breast cancer risk is complicated and multifactorial. The high risk appears to be connected to the estrogen production by the fat cells.
In premenopausal women, estrogen is mainly produced by the ovaries. However, in postmenopausal women, adipose tissues or fat tissues is the main source of estrogen production.
The number of fat cells is higher in overweight or obese women. This results in increased estrogen production, which is a risk factor for breast cancer development. This is especially of significance for Hormone-Receptive breast cancers that develop and grow on exposure to estrogen.
It has been found that women who are obese after menopause are at a 30% higher risk of developing breast cancer. Gaining more than 22 pounds after menopause can increase the risk of breast cancer by 18%.
Studies report an association between obesity and a lower risk of Estrogen-Receptor Positive (ER-Positive) breast cancer but a higher risk of ER-negative and Triple-negative breast cancer in premenopausal obese women.
In addition, a study from the Breast Cancer Surveillance Consortium database showed that obesity is associated with an increased risk for Inflammatory Breast Cancer (IBC) in premenopausal women.
The Million Women Study followed 1.2 million UK women ages 50 to 64 years for a mean of 5.4 years. Out of these, 45,037 women had breast cancer. The study identified a nearly 30% higher risk of developing postmenopausal breast cancer with obesity.
A meta-analysis of 34 studies reported that the risk of postmenopausal breast cancer increases with every 5kg/m2 increase in BMI.
Obesity affects the prognosis and survival rate of breast cancer patients. A recent study found that obese women with breast cancer experienced an 11% decrease in overall survival rate, irrespective of their menopausal status.
Besides breast cancer, obesity is a risk factor for type 2 diabetes and heart diseases - the latter seems to be the leading cause of mortality in women with early-stage breast cancer.
It has also been observed that obese women with breast cancer are more likely to experience complications during surgery and radiation.
In addition, systemic chemotherapy and endocrine therapy for treating breast cancer are less effective in obese women, further reducing prognosis and survival rate.
Breast cancer-specific mortality among obese women is 1.3 times higher compared to women with a normal BMI.
The mortality rate in obese women is also dependent upon the type and characteristics of the tumor. For example, obese women with Luminal A and Luminal B breast cancer were 1.8 and 2.2 times more likely to die from cancer than normal-weight women.
However, obesity was not associated with breast cancer-specific mortality among women with HER2- and triple-negative tumors.
BRCA1 Interacting Helicase 1 (BRIP1) is located on chromosome 17 and, along with the BRCA1 gene, helps repair any damage to the DNA. It is also responsible for maintaining chromosomal stability.
rs16945628 is a Single Nucleotide Polymorphism (SNP) in the BRIP1 gene. The TT genotype of this SNP is associated with an increased risk of breast cancer in women with a BMI of ≧25 kg/m2.
Insulin-like Growth Factor Binding Protein 3 or IGFBP3 gene is located on chromosome 7 and participates in cell growth, multiplication, and differentiation, and cancer development in the breast tissue.
rs2854744 is an SNP in the IGFBP3 gene linked to the risk of breast cancer. The CC genotype of this gene significantly increases the risk of breast cancer compared to the AA genotype. This increase was found to be more pronounced in older women.
Studies also showed that women carrying the AC+CC genotypes of the IGFBP3 gene had a larger tumor size in the breast.
Obesity is a critical non-genetic risk factor for breast cancer.
Other factors that increase breast cancer risk in obese women are:
According to a 2019 study, sustained weight loss is associated with lower breast cancer risk for women aged 50 years and older.
The researchers looked at 180,885 women from 10 studies. The women's weights were recorded 3 times over a period of 10 years; once when they enrolled and once every 5 years.
Weight changes of 2 kilograms or less (about 4.4 lbs) were counted as stable.
The study reported the following*:
*Compared with those whose weight was stable.
The study did not include women on postmenopausal hormone therapy, and the results were more prominent in obese or overweight women.
Despite this, the study suggests that even a modest amount of sustained weight loss can lower your breast cancer risk and improve survival rate, if diagnosed with breast cancer.
Diet is as important to mental health as it is to physical health. Previous studies have reported that the "traditional" dietary pattern, loaded with vegetable oil, meat, salt, and organ meat, is associated with increased odds of anxiety and depression in women. A recent study by researchers at the Ruhr-University Bochum and University of Duisburg, Germany, has reported higher depression scores among vegetarians than non-vegetarians.
Depression is a common yet serious mental condition that negatively impacts how you feel, the way you think and act. Depression occurs as a result of a combination of social, psychological, and biological factors.
Some of the common symptoms of depression are :
Depression susceptibility is related to diet both directly and indirectly. Unhealthy eating patterns can cause mood swings. When you stick to a healthy diet, you are setting yourself up for fewer mood fluctuations.
In particular, sugar is considered a major culprit. When consumed in higher quantities, it causes a temporary spike in 'feel-good' hormones like dopamine, which is not good for your health. In addition, the fleeting sugar rush followed by a crash is terrible for your mood.
A German research team conducted a meta-analysis on depression and vegetarian diet.
Meta-analysis refers to a procedure where the information collected from different experiments (with the same objective) is put together and studied. This combines the results of multiple studies to form a conclusion.
The analysis included data from 49,889 participants, of which 8,057 were vegetarians, and 41,832 were non-vegetarians. The large sample size makes this a robust study.
The researchers observed a higher depression score among vegetarians when compared to the non-vegetarians. But there was no causal relationship observed between them. That is, there was no proof that a vegetarian diet directly causes depressive moods. Depression didn't seem to increase a person's chance of adopting a vegetarian diet either.
This study, however, showed that it might be more likely that people switch to a vegetarian diet after developing mental health issues. The researchers cite three possible reasons for this:
A research study on the data from Adolescent Brain Cognitive Development (ABCD) Study suggests a relationship between certain regions in the brain and weight gain among children and adolescents. The study explored the relationship between “reward region” and food processing and suggests that this region may predict obesity in children.
Childhood obesity is a serious problem in the United States, putting children and adolescents at risk for poor health. Overweight children are much more likely to become overweight adults unless they adopt and maintain healthier patterns of eating and exercise.
Previous research has identified a region in the brain associated with overeating or unhealthy eating behavior.
Almost all our actions are driven by two things: Necessity and Reward. An activity can be considered a reward when it motivates us or gives us pleasure. Neurons, the brain's fundamental working unit, communicates this "reward" using dopamine, which is popularly known as the "happy hormone."
Incidentally, food-reward is common in animal training routines. An animal is rewarded with a treat when it performs certain actions and this programming of food-reward is routinely used by animal trainers in zoos and entertainment venues and other animal training facilities.
Hedonic hunger describes eating for pleasure than hunger - to enjoy the taste rather than to meet the body's energy needs. This pleasure eating triggers the brain's reward system region, which can lead to overeating - a common cause of obesity.
"The ABCD study or the Adolescent Brain Cognitive Development Study is the largest long-term study of brain development and child health in the United States." The study was done on over 10,000 children from ages 9-10 and was followed up through early adulthood.
Using the data from this study, the researchers attempted to investigate the relationship between the reward system region in the brain (called the nucleus accumbens) and eating behavior by examining 5300 research participants.
It was observed that when 2000 participants returned for a one year follow up, the waist circumference had increased by an average of 2.76 centimeters per participant.
The cell density (number of cells for a given area) in the reward region of the brain was examined using a noninvasive MRI technique.
The MRI revealed changes in the cell density that reflected the increase observed in the waist circumference.
The study speculates that the increase in this cell density can be because of an inflammation caused due to a diet rich in high-fat foods.
The findings essentially tell us that a vicious cycle of pleasure eating leading to changes in brain, in turn leading to overeating and increasing the risk of obesity.
Not all children who carry a few extra pounds can be classified as obese. Weight fluctuations are commonly observed in the growing stage of children. Before you decide on dietary changes for your child based on any weight gain you see, it's best to consult a doctor. The doctor may use growth charts, calculate the BMI and, take a family history, and, if necessary, may order a few tests to outline the issue behind the weight gain.
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