More new cancer cases linked to obesity

A recent study found that obesity caused 500,000 new cancer diagnoses worldwide in just one year. Carrying too much weight is already a known risk factor for certain cancers, but the findings suggest obesity may play an even greater role.

For a reminder of the importance of diet and exercise to help prevent disease, look no further than a recent study in The Lancet Oncology. Researchers attributed 500,000 new cancer cases worldwide in just one year to obesity. Carrying too much weight is already a known risk factor for certain cancers, including breast cancer, colorectal cancer and pancreatic cancer. But the findings suggest obesity may play an even greater role. 

The study involved thousands of people from 184 countries over a 10-year period, starting in 2002 when researchers collected the body mass index (BMI) of study participants. BMI uses height and weight to calculate body fat. For example, anyone who is 5 feet 5 inches and weighs 180 lbs. or more would be classified as obese. Similarly, someone who is 6 feet and weighs 221 lbs. or more is considered obese.

In 2012, researchers calculated that 3.6 percent of new cancer cases that year, excluding non-melanoma skin cancer, could be attributed to increasing BMI among study participants. They found that North America had the highest rate of cancers caused by obesity: 111,000 new cases in 2012, with nearly 10 percent of diagnoses among women linked to obesity.

Obesity in the United States has increased in the past 25 years, while tobacco use has fallen. Now, more than 33 percent of American adults are obese and about 18 percent of adults smoke. In 1990, about 11 percent of adults were obese and nearly 26 percent smoked. Obesity may soon replace tobacco use as the leading preventable cause of cancer, according to the American Society of Clinical Oncology.

There are several explanations of why obesity may promote cancer development:

  • The hormone insulin-like growth factor, IGF-1, stimulates cell growth in obese people at possibly at twice the rate of normal-weight people, which may promote tumor growth.
  • People who are obese have higher amounts of the hormone leptin, which appears to promote cell proliferation, and less of the hormone adiponectin, which may prevent cell growth.
  • Fat tissue produces high levels of the hormone estrogen, which has been associated with the risk of breast and uterine cancers.
  • Fat cells may affect other tumor growth regulators, such as mammalian target of rapamycin (mTOR) and AMP-activated protein kinase.
  • People who are obese often have chronic low-level inflammation, which has been associated with increased cancer risk.
  • Microbes that live in the gut of obese people activate bacteria to secrete chemicals that damage DNA and lead to tumor growth.

Losing weight can be challenging, but people who are obese can achieve significant and sustained weight loss through a combination of diet, physical activity and stress management. “Now more than ever, we can view cancer as a disease we can work to prevent by keeping our BMI in check,” says Nhu Huynh, Director of Nutrition at our hospital in Philadelphia. Huynh suggests eating more fiber-rich foods and adding prebiotics to your diet as nutritional strategies to maintain a healthy weight.

  • Dietary fiber can help you achieve greater weight loss by making you feel fuller longer. You’ll eat less during a meal and won’t snack as much between meals. It also enhances how your body metabolizes glucose (blood sugar), decreases inflammation and promotes beneficial changes in intestinal microbiota. Sources of fiber include fruit, vegetables, beans, nuts and whole grains (brown rice, whole wheat bread, oatmeal).
  • Prebiotics are nondigestible carbohydrates that promote the growth of good bacteria in the intestines to help you maintain a healthy digestive system. Prebiotics occur naturally in a number of high-fiber foods such as bananas, oatmeal, asparagus, Jerusalem artichokes, beans, leeks and onions.

Learn the nutritional advantages of Mediterranean diets.