First off, they TYPES of cancer more commonly related to weight are:
- After menopause breast cancer
- Pancreas
- Colon
- Esophagus
- Endometrium (lining of the uterus)
- Gallbladder
- Kidney
- Thyroid
Now the HOW:
While researching this post, I have found it difficult to find medical literature that empirically states through which physiological mechanisms obesity increments the risk of cancer. What I have found are "possible mechanisms" that suggest an explanation for the association of obesity with increased risk of certain cancers.
1. Fat tissue produces increased amounts of estrogen. High levels of this hormone have been associated with the risk of breast and endometrial cancers, and some others.
2. Obese people tend to have increased levels of insulin and IGF-1 (Insulin like growth factor 1) in their blood, this is a condition called hyperinsulinemia or insulin resistance, which is thought to promote the development of certain tumors. High levels of insulin can promote cancer growth through interaction with tumor cells' insulin receptors and/or IGF-1 receptors.
3. Fat cells produce hormones, called adipokines, that are thought stimulate or inhibit cell growth. Leptin, for example, is more abundant in obese people and seems to promote cell proliferation, whereas adinopectin may have the opposite anti-proliferative effect, but is less abundant in obese people.
4. Fat cells may also have indirect and direct effects on tumor growth regulators including
mammalian target of rapamycin (MTOR) and AMP-activated protein kinase.
5. Obese people usually have chronic low-level inflammation, which has been associated with an increased risk of cancer.
A study using NCI Surveillance, Epidemiology, and End Results (SEER) data, estimated that in 2007 in the USA 34,000 of new cancers (4%) in men, and 50,500 (7%) in women were due to obesity. Depending on the type of cancer the percentage of cases attributed to obesity varied widely, but was as high as 40% for some cancers, in particular endometrial cancer and esophageal adenocarcinoma.
A projection for future health and economic burden from obesity by 2030 estimated that if the existing trends in obesity continue, then there will be an extra 500,000 cases of cancer in the US alone by 2030.
It is very complicated to prove that losing weight or avoiding weight gain would lower cancer risk - clinically that is. Previous trials and the results of a National Cancer Institute workshop have shown that it wouldn't be feasible to conduct a cancer prevention via weight loss trial. This is because the effect of weight loss on the prevention of other chronic diseases would be demonstrated BEFORE the effect on the prevention of cancer would become evident, so the trial would be stopped too soon in order to inform the public of the benefits of weight loss on chronic disease... why they couldn't release that information and continue on with the trial I have no idea...
Most of the current data on preventing cancer through weight loss or avoiding weight gain, come from cohort and case-control studies. Data from these observational studies can be difficult to interpret because people who lose weight or do not gain weight may be different in other ways (physiologically) than people who do not. In the same way that obese people may differ from lean people in other ways than just their BMI.
However, many observational studies have shown that people who have a lower weight gain during adulthood have a lower risk of colon cancer, post menopausal breast cancer and endometrial cancer.
So, it is in your hands to look after yourself and keep your cancer risk in check!
I can help you improve your health. If you would like to make an appointment with me either in person or via Skype, just send me an email to lucycarr@socialnutrition.com
4. Fat cells may also have indirect and direct effects on tumor growth regulators including
5. Obese people usually have chronic low-level inflammation, which has been associated with an increased risk of cancer.
A study using NCI Surveillance, Epidemiology, and End Results (SEER) data, estimated that in 2007 in the USA 34,000 of new cancers (4%) in men, and 50,500 (7%) in women were due to obesity. Depending on the type of cancer the percentage of cases attributed to obesity varied widely, but was as high as 40% for some cancers, in particular endometrial cancer and esophageal adenocarcinoma.
A projection for future health and economic burden from obesity by 2030 estimated that if the existing trends in obesity continue, then there will be an extra 500,000 cases of cancer in the US alone by 2030.
It is very complicated to prove that losing weight or avoiding weight gain would lower cancer risk - clinically that is. Previous trials and the results of a National Cancer Institute workshop have shown that it wouldn't be feasible to conduct a cancer prevention via weight loss trial. This is because the effect of weight loss on the prevention of other chronic diseases would be demonstrated BEFORE the effect on the prevention of cancer would become evident, so the trial would be stopped too soon in order to inform the public of the benefits of weight loss on chronic disease... why they couldn't release that information and continue on with the trial I have no idea...
However, many observational studies have shown that people who have a lower weight gain during adulthood have a lower risk of colon cancer, post menopausal breast cancer and endometrial cancer.
So, it is in your hands to look after yourself and keep your cancer risk in check!
I can help you improve your health. If you would like to make an appointment with me either in person or via Skype, just send me an email to lucycarr@socialnutrition.com
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