Looking for ways to reduce your risk of cancer? Try losing weight.
A new study estimates that 3.6% of cancers diagnosed around the world in 2012 could be traced to the excess weight of patients. That works out to 481,000 cases of cancer in adults who were at least 30 years old, according to the report in Lancet Oncology.
About 23% of these cancers were diagnosed in North America, where the proportion of cancers that could be traced to people’s extra pounds was highest. An additional 14% of these weight-related cancers were diagnosed in East Asia, where the risk due to extra weight was low but the population is so large that the patients added up.
The international research team found that countries with a “high” or “very high” human development index – a measure of a nation’s wealth known as HDI – could blame a higher fraction of their cancers on extra weight than could countries with a “moderate” or “low” HDI. In fact, the proportion of cancers linked to excess weight in the richest countries (5.3%) was more than five times higher than the proportion for the poorest countries (1%).
The researchers focused on nine types of cancer that have been linked with excess weight in previous studies. These include cancers of the esophagus, colon, rectum, kidney, pancreas, gallbladder, uterus and ovaries, as well as postmenopausal breast cancer. Patients were considered overweight if they had a body mass index of 25 of higher.
The team used data from the GLOBOCAN project to find cancer rates around the world in 2012, sorted by country and gender. They limited their analysis to adults who were 30 or older based on the premise that it takes about 10 years for extra pounds to do the biological damage that increases cancer risk. As such, they used BMI data from 2002 for adults who were at least 20 years old at that time.
The researchers found that being overweight or obese raised cancer risk much more for women than for men. Overall, 5.4% of the new cancers in women could be traced to high BMIs, compared with 1.9% of new cancers in men. In women, the proportion of cancers linked to excess weight was highest in Barbados (at 12.7%), the Czech Republic (12%) and Puerto Rico (11.6%); in men, the highest rates were seen in the Czech Republic (5.5%), Jordan and Argentina (4.5%) and the United Kingdom and Malta (4.4%).
Postmenopausal breast cancers and uterine cancers accounted for about two-thirds of all new cancers linked to high BMI in women, while cancers of the colon and kidneys made up two-thirds of such cancers in men.
If the global population had not gotten fatter since 1982, roughly 118,000 cancers that were newly diagnosed in 2012 could have been avoided, the researchers calculated. That’s almost 1 in 4 cancers that were found that year.
But the world did get fatter. And the situation is getting worse, not better.
“The continuation of current patterns of population weight gain will lead to continuing increases in the future burden of cancer,” the researchers concluded.