Key TakeawaysObesity in 20- to 39-year-olds may be associated with a higher risk of developing cancer within 10 yearsRisk increases as obesity becomes more severeThyroid, endometrial and ovarian cancers show some of the strongest associations with obesity.WEDNESDAY, Oct. 28, 2026 (HealthDay News) — Having obesity in your twenties and thirties could raise your risk for early-onset cancer.A team led by Dr. Jae-Seung Yun of The Catholic University of Korea in Seoul followed more than 6 million adults, ages 20 to 39, for about a decade. All were healthy when the study began.Among participants at a normal weight, 1.8% developed cancer within 10 years.Among those with obesity, the number rose to 2.2%. And with more severe obesity, it jumped to 2.6%. Belly fat mattered, too. People with excess abdominal fat had the highest cancer rates overall, researchers found..Thyroid, endometrial and ovarian cancers showed some of the strongest links, according to the results.Researchers did not find a significant link with breast cancer, however.This study cannot prove cause and effect, and the authors acknowledged limitations, including a lack of detailed smoking data.Still, they said the findings highlight the importance of managing weight early in adulthood.More research is needed to determine whether intentional weight loss reduces cancer risk.The study was published Oct. 27 in the Annals of Internal Medicine.More informationThe U.S. Centers for Disease Control and Prevention has more on obesity and cancer.SOURCE: HealthDay TV, Oct. 28, 2026 .What This Means For YouMaintaining a healthy weight in your twenties and thirties may help lower your risk of developing certain cancers..Sign up for our weekly HealthDay newsletter