40% of cancer diagnoses linked to excess weight

Here’s one more reason to reach a healthier body weight – a new report from the Centers for Disease Control and Prevention (CDC) says cancers associated with being overweight or obese account for 40% of all diagnoses of the disease in the United States. 

The good news since the 1990s, is that new cases of cancer have fallen.  The bad news is diagnoses of overweight – and obesity-linked cancers increased between 2005 and 2014.  Since the mid-20th century the rate of Americans who are considered overweight by the CDC has steadily climbed and now stands at two out of three people. In 2014, about 630,000 people in the US were diagnosed with overweight- or obesity-linked cancer with two-thirds of those cases found in adults between 50 and 74. 

This study looked at cancers more likely to occur in people who are overweight or obese or who have a body mass index or BMI of at least 25 or higher.  The report was careful to say that these cancers they reviewed are linked to carrying excess body weight but are not necessarily caused by being overweight or obese.

This may be news to many Americans as individuals often think there is little they can do to prevent cancer. However other recent reviews have shown that carrying excess body fat raises the risk of 13 different types of cancer.  Researchers are now saying that next to smoking, maintaining a healthy body weight is the most important thing people can do to lower their risk of cancer.  Making other lifestyle changes is another modifiable thing most people can do to also lower their chance of developing cancer.

Why body fat may be linked to cancer

When a person gains weight, the excess weight is stored as body fat.  We may think of body fat as being relatively inactive but this is not true.  Excess body fat has more influence than once realized – it can affect the levels and metabolism of hormones such as insulin and estradiol which in turn effects functioning of the immune system and raises inflammation.  This type of activity enhances cell growth while discouraging cell death which is how cancer can begin.

A good example of how having too much body fat can influence hormones is the hormone estrogen.  After a woman has gone through menopause, if she is carrying excess body fat, it will be the main site of estrogen synthesis.  This leads to excess estrogen levels which increase the risk of hormone-related cancers such as breast and endometrial cancer. 

Another example is when someone has excess abdominal fat which increases insulin resistance.  This results in high circulating blood glucose which requires the hormone insulin to help unlock the doors to the cells of the body to be removed from the bloodstream.   The pancreas then has to compensate by producing more insulin which can lead to hyperinsulinemia which may raise the risk of certain types of cancer.

Just having excess body fat can lead to other secondary problems that could lead to a greater risk of some cancers. For example, people who are overweight to obese are more likely to develop gastroesophageal reflux disease and gallstones, which can increase the risk of esophageal/stomach cancers and gallbladder cancer. 

Cancers linked to body fatness

Approximately 13 cancers identified by both the CDC and the International Agency for Research on Cancer (IARC)  have been found to be linked to body fatness.  They include the following:

·      Multiple myeloma

·      Spinal cancer called meningioma

·      Breast

·      Colon and rectum

·      Esophagus

·      Gallbladder

·      Kidney

·      Liver

·      Ovarian

·      Endometrium

·      Pancreas

·      Stomach

·      Thyroid

The American Institute for Cancer Research has stated that in the United States, maintaining a healthy body weight can prevent the following cancers:

·      22% of gallbladder cancers

·      11% of advanced prostate cancers

·      5% of ovarian cancers

·      33% of esophageal cancers

·      19% of pancreatic cancers

·      Around 24% of kidney cancers

The American Institute for Cancer Research also stated that maintaining both a healthy body weight and being active can prevent the following:

·      50% of colorectal cancers

·      33% of breast cancers

·      30% of liver cancers

·      59% of endometrial cancers

What can individuals do to reduce body fat and risk of cancer?

For anyone who is already overweight to obese, there are always lifestyle modifications that can be done to help reduce the risk of cancer.  Even modest weight loss improves factors associated with cancer risk such as improving insulin sensitivity and reducing inflammation.  Any amount of weight loss has health benefits making weight loss a good idea. 

Here are some suggestions from the World Cancer Research Fund International anyone can do to get started on leading a healthier lifestyle leading to a healthier body weight and a reduced risk of cancer:

·      Keep weight within a healthy range

·      Be physically active for at least 30 minutes every day and sit less often

·      Avoid high-calorie food and sugary drinks

·      Eat more whole grains, fruits, vegetables and beans

·      Limit red meat and avoid processed meat

·      For cancer prevention, limit or avoid alcohol beverages

·      Eat less salt

·      For cancer prevention, don’t rely on supplements

·      If you can, breastfeed your baby for at least six months