WEDNESDAY, Dec. 12, 2018 (HealthDay News) -- Overweight and obesity accounted for nearly 4 percent of all cancers globally in 2012, and that rate is likely to rise in coming decades, a new study suggests.
Rates of excess body weight have been increasing worldwide since the 1970s. By 2016, about 40 percent of adults (2 billion) and 18 percent of children aged 5 to 19 (340 million) had excess body weight, the researchers said.
Some of the largest increases in overweight and obesity have been in low- and middle-income countries. That's likely due to the spread of a "Western" lifestyle that includes fatty, sugary foods and lower levels of physical activity, the study authors noted.
One U.S. obesity expert wasn't surprised by the new numbers.
Someday, "obesity is going to surpass cigarette smoking as the leading cause of cancer deaths," said Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York City. "The links between obesity and cancer are becoming clearer."
The new report was drafted in part by scientists at the American Cancer Society (ACS), and published online Dec. 12 in CA: A Cancer Journal for Clinicians.
The study found that in 2015, about 4 million deaths were attributable to excess body weight.
According to lead researcher Hyuna Sung and colleagues at the ACS, the spread of Western lifestyles has led to a "rapid increase in both the prevalence of excess body weight and the associated cancer burden."
Looking at global data for 2012, excess body weight accounted for nearly 4 percent (544,300) of cancers worldwide, with rates ranging from less than 1 percent in poor nations to 8 percent in some wealthy Western countries and in Middle Eastern and northern African countries, the findings showed.
Overweight and obesity has been linked to an increased risk of a number of cancers: breast, colon, esophagus, gallbladder, kidney, liver, ovary, pancreas, stomach, thyroid, meningioma and multiple myeloma, according to the study.
Piling on too many pounds has also been linked to advanced prostate cancer and cancers of the mouth, pharynx and larynx, the researchers said in a journal news release.
Roslin agreed that obesity exerts hormonal effects that can, in turn, encourage cancer.
"Obesity changes fat-soluble hormone levels, explaining the link to postmenopausal breast cancers," he said. "Additionally, obesity increases insulin, glucose and insulin growth factors," which can also heighten cancer risk.
"This creates a perfect environment for cancer cells to grow. So in addition to an increased prevalence of certain cancers, obesity makes cancers grow faster and be less treatable," Roslin explained.
Sung's team believes the report calls for a "rejuvenated focus" on steps that could help curb the spread of obesity, such as banning trans fats, taxing sugary beverages, limiting average portion sizes, and making communities more walkable and bicycle-friendly, so people move more.
The U.S. National Cancer Institute has more on obesity and cancer.