Obesity in Your 20s and 30s May Increase Cancer Risk Later in Life

New research shows that having obesity in your 20s and 30s may increase your risk of developing cancer before midlife. Anchiy · E+/Getty

• Young adults with obesity may face a higher risk of developing cancer before midlife compared to those at a moderate weight, according to new research.
• Cancer risk increased progressively with weight, from 1.84% in people at a moderate weight to 2.62% in those with severe obesity.
• Abdominal obesity (measured by waist circumference) was also linked to elevated cancer risk, even in people with moderate weight.
• Weight management through diet, exercise, and medications may help reduce cancer risk.

Younger adults with obesity may be more likely to develop cancer before midlife than those who maintain a moderate weight, according to a study published on October 26 in the Annals of Internal Medicine. 

The risk for cancer became higher as weight increased. The highest rates were seen in those with severe obesity and abdominal obesity. 

This highlights the potential importance of weight management in the prevention of early onset cancer. 

Obesity in young adulthood increases risk of cancer

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. 

Body mass index (BMI) was categorized into five groups ranging from underweight to class II obesity using the World Health Organization (WHO) criteria for Asian populations. Waist circumference was also measured as an indicator of abdominal adiposity. 

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: 

• thyroid
• endometrial
• ovarian
• colorectal
• kidney
• liver
• pancreatic

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. 

Obesity-cancer connection is a global issue

This current study focused on the Korean population. However, the connection between obesity and cancer risk is a global issue. 

Previous research has shown that around 10% of all new cancer diagnoses in the United States are associated with obesity. Obesity also accounts for up to 50% of certain cancers, including endometrial and liver cancer. 

Waist size matters even at a moderate weight

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 National Heart, Lung, and Blood Institute (NHLBI), waist circumference measurements that can increase your risk of negative health issues are 101.6 cm (40 in) for males and 88.9 cm (35 in) for females. 

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.  

People who have smoked may face higher cancer risk

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.