According to a study carried out by the World Health Organisation, obesity has become the biggest preventable risk factor for cancer in Australia after smoking.
Cancer is the world’s biggest killer, with 8.2 million deaths as a result of the disease every year. While Australia fares reasonably well compared to other countries in terms of deaths, it does have one of the highest cancer incidence rates, coming in third behind Denmark and France.
According to Cancer Council Australia, there are several factors behind the country’s high rate of cancer incidences: an ageing population, superior screening and vaccination programs, and the growing obesity epidemic associated with a Western lifestyle.
Should risk factors such as obesity not be tackled quickly, it is expected that the number of cancer cases will increase by 75% over the next two decades.
The link between obesity and cancer
Obesity is associated with (but not restricted to) increased risks of the following cancer types:
- Colon and rectum
- Postmenopausal breast
- Endometrial (lining of the uterus)
There is multiple mechanisms likely linking obesity to cancer:
Fat tissue produces excess amounts of oestrogen. Oestrogen has long been seen as a carcinogen, with strong epidemiological evidence pointing to the hormone as a cause of breast, endometrial, and uterine cancers.
Increased levels of insulin. Insulin is an important growth factor for body tissues, but this also means that high levels of insulin can promote the development of certain tumours - particularly in the colon, breast and pancreas. This is due to the high number of insulin receptors that are displayed by tumours, particularly those found in breast cancer growths.
Hormones that stimulate or inhibit growth. Fat cells produce certain types of hormones that can promote cell proliferation. These hormones are directly associated with breast cancer development, as they help abnormal/cancerous cells grow quicker and more aggressively.
High blood pressure. High blood pressure is a known risk factor for renal cell cancer.
Chronic low-level inflammation. Chronic inflammation can be triggered by excessive calorie consumption and can contribute significantly to the deterioration associated with the ageing process, eventually leading to some cancers.
What is obesity?
Obesity is defined as abnormal or excessive fat accumulation that may impair health. Commonly defined by body mass index (BMI), a person’s weight in kilograms is divided by the square of height in metres. Obesity is classified as a BMI greater or equal to 30.
It is estimated that 3.4 million adults die globally each year as a direct result of being overweight or obese. In addition, 44% of diabetes cases, 23% of ischemic heart disease cases and up to 41% of certain cancers are attributed to obesity.
Overall, it is estimated that 30% of the global population is obese.
Why is obesity preventable?
A person becomes obese through the lifestyle choices they make. When we consume food and drink that contains more energy (kilojoules) than the energy used in activity and rest, the fat is deposited on the body. With regular imbalances, the body can become obese.
- Preventable factors associated with obesity include:
- Eating excess kilojoules
- Modern conveniences (cars, televisions, computer games etc)
- Socioeconomic factors
- The marketing of nutrient-poor food
How to prevent obesity
The best way to control obesity is to educate people on the importance of choosing healthier, lower-energy foods. This includes a variety of wholegrain, wholemeal and high-fibre foods - such as cereals, breads, rice and pasta. It also includes at least two serves of fruit and five serves of vegetables a day, limited amounts of processed meat, and limited alcohol.
It is also important to be physically active for at least 30 minutes a day.
Can reducing weight lower the risk of cancer?
A Swedish study carried out over a 10 year period observed the health of more than 4,000 very obese people (with a body mass index of above 34). Of this group, half were treated with bariatric surgery, designed to help them lose weight, while the rest were given lifestyle advice to help them on their healthier path.
After 10 years, the participants that lost 20kg reduced their overall risk of cancer by a third. Women experienced a higher result than men, experiencing a 42% drop in their cancer risk.
Though no long-term studies have been published by Australian researchers regarding the link between obesity and cancer, the Centre for Obesity Research and Education (CORE) at Australian institute Monash University is dedicated to undertaking new research and managing obesity, which they classify as a chronic disease. Their primary purpose is to better understand obesity as a condition, and how weight loss can affect health, quality of life and survival rates in our society. As leaders in the Australian medical field of clinic and psychological research into obesity and weight loss, it is only a matter of time before CORE becomes a significant provider of obesity-related research in the international community.
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