A Swedish study involving more than 600,000 patients has revealed that gaining weight as an adult increases the risk of developing cancer by up to five times. The research, conducted by Lund University, analyzed weight and cancer incidence data from over 250,000 men and nearly 380,000 women, measuring their weight an average of four times between ages 17 and 60. Cancer diagnoses were tracked until 2023.
Key Findings on Weight and Cancer Risk
The study found that increased cancer risk, both overall and for many specific types, was associated with heavier initial weight in early adulthood as well as weight gained during adulthood. Lead author Anton Nilsson stated, "The higher the starting weight and the greater the weight gain, the higher the cancer risk tended to be." Men who became obese before age 30 had a five times higher risk of liver cancer, double the risk of pancreatic and kidney cancer, and a 58% increased risk of colon cancer compared to those who remained slim. Women who developed obesity before age 30 faced a four-and-a-half times increased risk of endometrial cancer, a 67% higher risk of pancreatic cancer, double the risk of kidney cancer, and a 76% increased risk of meningioma.
Gender Differences in Later Weight Gain
For those who gained weight later in life, gender differences emerged. Among women, weight gain after age 30 was strongly linked to increased risks of endometrial cancer, postmenopausal breast cancer, and meningioma—cancers where sex hormones are considered a primary factor. Colon cancer was also strongly associated with female weight changes. In men, associations with obesity-related cancers were stronger for weight gains before age 45, particularly for esophageal and liver cancer. Nilsson explained this may be because earlier weight gain allows more time for biological processes like inflammation and raised insulin levels to affect susceptible tissues.
Weight Gain Amount and Cancer Risk
Those who gained the most weight (an average of 32 kg or 5 stone) were 7% more likely to develop cancer than those who gained the least (average 8 kg). Men with the highest weight gain were nearly three times more likely to develop liver cancer and more than twice as likely to develop esophageal cancer. They also had three times the risk of pituitary tumors and a more than 50% increased risk of renal cell carcinoma, gastric cardia, and colon cancers. Women with the highest weight gain had nearly four times the risk of endometrial cancer, double the risk of pituitary tumors, and significantly higher risks of renal cell carcinoma (91%), postmenopausal breast cancer (42%), meningioma (32%), and colon cancers (31%).
Even lower amounts of weight gain increased cancer risk, underscoring the need to avoid excess weight. Nilsson added, "While our results do not speak to any specific interventions or behaviors, they highlight the importance of maintaining a stable, healthy weight throughout adult life." Megan Winter of Cancer Research UK commented, "Overweight and obesity is the second biggest cause of cancer in the UK. The government should do more to help people find it easier to keep slimmer. Further measures to restrict the advertising and promotion of junk food, introduce mandatory reporting on healthy food sales, and make nutritious food more accessible to everyone could all help reduce obesity rates and improve health across the country."
