Rates of both obesity and early onset cancer are rising among younger adults globally.
This study analyzed data from the Korean National Health Insurance Service database. The researchers identified 6,313,338 adults ages 20 to 39 who had no history of cancer and who underwent standardized national health screenings.
The researchers followed the participants for an average of 11 years.
During the analysis, the researchers adjusted for various factors such as:
- age
- sex
- smoking status
- alcohol consumption
- physical activity
- income
- residential area
- metabolic comorbidities, like hypertension, diabetes duration, glucose tolerance, and dyslipidemia
Over the follow-up period, there were 151,893 cases of cancer among the participants. The incidence rate increased progressively based on obesity categories, from 1.84% in “normal-weight” individuals to 2.24% in class I obesity and 2.62% in class II obesity.
The strongest associations were seen in the following cancers:
Obesity was not associated with breast cancer diagnosed before the age of 50.
Ketan Thanki, MD, board certified colorectal surgeon with the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, who wasn’t involved in the study, explained to Healthline that obesity itself causes states that promote cancer formation.
The study also showed that waist circumference, which indicates abdominal obesity, may be linked to cancer risk that is similar to that of individuals with overweight.
The study researchers used the thresholds set out by the Korean Society for the Study of Obesity. These thresholds put the waist circumference cutoff at over 90 cm (35.4 in) for males and over 85cm (33.46 in) for females.
These are not universal cutoffs. According to the
Previous research has also suggested an association between waist circumference and cancer risk, independent of BMI. One study showed a potential 11% increased risk of cancer in people with a waist circumference over the thresholds, even if they were physically active.
The current study found that males had a higher relative association between obesity and cancer, while females showed higher absolute risk.
The researchers also found that the absolute risk was higher in adults ages 30 to 39.
Those who currently smoke or who have ever smoked were also found to have a higher risk of developing cancer than those who have never smoked.
“Diet, exercise, and now medications can all be used very effectively to reduce one’s weight and, hopefully as a result, cancer risk,” Thanki said.
He also noted that, due to differences between South Korean populations and those in other countries such as the United States, further studies will be needed to determine how this translates across other populations.
“But I think this trend will likely extend across all cultures,” he said.
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