Cancer & Obesity

Did you know that more than two thirds (67%) of Australian adults are considered to be overweight or obese? That’s a staggering 12.5 million people!

It is clear that we are living in a society where overweight and obesity are becoming increasingly the social norm, even though a growing amount of our evidence has shown that excess weight can increase the risk of serious health consequences.

Cardiovascular disease, asthma, back and joint problems, chronic kidney disease, dementia and diabetes have all long been linked to excess weight. But did you know overweight and obesity are also strongly linked to an increased risk of developing cancer?

Each year in Australia, 5300 new cancer diagnoses are contributed to an overweight or obese status. In fact, those living with excess weight have a higher risk of developing 13 different types of cancers. These include cancers of the oesophagus, breast, colon and rectum, uterus, gallbladder, stomach, kidneys, liver, ovaries, pancreas, thyroid, prostate and multiple myeloma.

How does obesity increase the risk of cancer?

It’s important to understand that body fat is not just stored under the skin, it is stored deep inside our bodies, surrounding our organs. This type of fat is called visceral fat or “toxic fat”. This type of fat has a bad reputation because it can change the environment inside our body by producing chemicals and hormones that cause neighbouring cells to begin acting differently and potentially becoming cancerous. Let’s look at the three main processes responsible for excess weight increasing cancer risk:


Those carrying excess weight often have higher levels of insulin in their blood. Excess body fat causes cells to become increasingly resistant to the effects of insulin, known as insulin resistance. This causes the pancreas to make even more insulin to try and compensate. This is known as hyperinsulinemia. It is insulin resistance and hyperinsulinemia that can over time affect the levels of growth factors, which cause cells to divide. It is both insulin and these growth factors that encourage uncontrolled cell division, promoting the development of cancer.

Inflammatory Response

Inflammation is the bridge between excess weight and cancer. Immune cells gather around large collections of fat cells and this leads to an inflammatory response. During the inflammatory response, they release chemicals known as cytokines. Cytokines encourage cells to divide more rapidly leading to a build-up of dead cells which can lead to cancer growth.


Fat cells release significant amounts of oestrogen (the more fat cells you have, the more oestrogen will be released). High levels of oestrogen can cause cells in the womb and breasts to divide uncontrollably leading to cancer.

How can I lower my risk?

One of the most important things you can do to decrease your risk of overweight or obesity-linked cancers is to work towards and maintain a healthy weight. There is consistent evidence that those who have a lower weight gain during adulthood have lower risks of cancers. Some studies have found decreased risks of cancers (specifically breast, endometrial, colon and prostate cancers) among those who have lost weight. There is also stronger evidence that those who were obese and have had bariatric surgery have lowered risks of obesity-related cancers compared to those who are obese and did not have bariatric surgery.

Easy tips to start reducing your risk

  1. Limit the portion size of your meals and snacks
  2. Choose wholegrain and high fibre cereals and breads
  3. Eat plenty of vegetables and fruit each day
  4. Cut out unhealthy snacks and replace these with healthy, whole foods i.e. nuts, yoghurt, cheese, fruit and vegetables
  5. Swap sugary drinks for water
  6. Limit alcohol
  7. Exercise regularly

There is strong evidence that being above a healthy weight is a risk factor for many different types of cancers. It has been found that if all Australians maintained a healthy weight, just under 200 000 overweight or obesity-related cancers could be prevented over a 25 year period. These results show that we have the potential to prevent a significant amount of cancers and potentially save hundreds of thousands of lives.

Tegan Tudor, WLSA Dietitian