New research presented at this year's European Congress on Obesity (ECO 2026) in Istanbul, Turkey (12-15 May) shows that people who gain the highest amount of weight across adulthood are at greatly increased risk of certain obesity related cancers. The study is by Associate Professor Anton Nilsson and Associate Professor Tanja Stocks, Department of Translational Medicine, Lund University, Malmö, Sweden, and colleagues.
Obesity affects one in eight individuals globally and is recognised as a leading cause of cancer. As highlighted by the International Agency for Research on Cancer (IARC), substantial evidence has linked excess body weight to cancers of the oesophagus (adenocarcinoma), gastric cardia (top part of the stomach), colorectum, liver, gallbladder, pancreas, postmenopausal breast, endometrium, ovaries, kidneys, meninges, thyroid gland, and multiple myeloma. Evidence of potential links to other cancer forms exists as well, including certain blood cancers.
Most studies on body weight and cancer have focused on weight at a single point in time – typically in mid to late adulthood – or on weight changes between two points. Associations between life-course weight patterns trajectories based on multiple weight assessments and the risk of developing cancer remain less explored. In this new study, the authors examined body weight trajectories from ages 17 to 60 and their associations with site-specific cancer incidence. Data were based on the ODDS study, a pooled, nationwide cohort study in Sweden, with data on weight spanning 1911 to 2020, and cancer follow-up through 2023. Data from 251,041 men and 378, 981 women were used, with each person having on average four weight measurements between age 17 and 60.
Steeper weight gain was associated with higher incidence of any cancer, as well as many established obesity-related cancers among both men (Figure 1 full paper) and women (Figure 2), with stronger associations the greater the weight gain. When comparing cancer risk in the top 20% of weight gain with the lowest 20% (reference), and for all cancers combined the increased risk of cancer in the highest 20% was 7% for men and 17% for women, whereas for established obesity-related cancer the increased risk was 46% in men and 43% in women.
For specific established obesity-related cancers, again for top 20% of weight gain versus bottom 20%, there was 2.67 times increased risk of liver cancer and a 2.25 times increased risk of oesophageal cancer among men, and a 3.78 times increased risk of endometrial cancer among women.
Smaller increased risks were seen for gastric cardia (61%) and rectal (16%) cancers among men, postmenopausal breast cancer (42%) and meningioma (32%) among women, and colon cancer and renal cell carcinoma among both men (52% and 81%) and women (31% and 91%).
Among cancers not yet established obesity-related, which have been indicated associated with obesity in previous work (eFigures 3-4), and again for top 20% of weight gain versus bottom 20%, substantial associations were seen for pituitary tumours among men (HR 3.13 times increased risk) and women (2.13 times), with significant associations also for malignant melanoma (27% increased risk) and diffuse large B-cell lymphoma (48%) among men, and tumours of the parathyroid gland (33%) among women.
Besides weight changes throughout adulthood in ages 17-60, weight before entering adulthood at age 17 was associated with several cancer types (eFigures 5-8). For most cancers, the increased risk comparing those with the highest 20% of weight and the lowest 20% at age 17 were comparable in magnitude to those for the top 20% versus bottom 20% of weight gain from age 17.
Early, middle, and later adulthood weight changes were associated with overall cancer incidence and established obesity-related cancers among both men (Figure 3) and women (Figure 4). For established obesity-related cancers combined, associations were stronger for early and middle adulthood weight gain among men but stronger for middle and later adulthood weight gain among women; when women's data was analysed without female-specific cancers, associations with weight increase were similar across all three age periods.
Some cancers were most strongly associated with early adulthood weight changes (particularly renal cell carcinoma among men), others with weight changes in middle adulthood (liver cancer among men and colon cancer among both sexes), and still others with later adulthood weight changes (gastric cardia cancer among men and meningioma among women). However, these were mostly non-statistically significant trends.
Analyses using age of obesity onset as the exposure (eFigures 10-11), revealed a tendency for cancer incidence to be more strongly associated with earlier ages of obesity onset. This pattern was particularly evident for liver and colon cancer among men, endometrial cancer and meningioma in women, and renal cell carcinoma and pancreatic cancer in both men and women. Men who developed obesity before age 30 years were at a 5-times risk of liver cancer, a doubled risk of pancreatic cancer and renal cell cancer, and a 58% increased risk of colon cancer compared with men who never had obesity. Women who developed obesity before age 30 years were at a 4.5 times increased risk of endometrial cancer, a 67% higher risk of pancreatic cancer, doubled risk of renal cell cancer, and a 76% increased risk of meningioma.
The authors say: "Steeper increases in body weight between ages 17 and 60 were associated with higher incidence of several established obesity-related cancers, as well as some for which previous evidence linking obesity to cancer is more limited. Associations were particularly pronounced for liver cancer and oesophageal adenocarcinoma among men, endometrial cancer among women, and renal cell carcinoma and pituitary tumours in both sexes."
They add that weight gain among women aged 30 years or older was strongly associated with endometrial cancer, postmenopausal breast cancer, and meningioma – cancers for which sex hormones are considered a primary etiological factor. Colon cancer was also strongly linked to female weight changes in these ages. Among men, the associations with established obesity-related cancers were instead stronger for weight gains below age 45, most clearly for oesophageal and liver cancer – cancers for which factors such as chronic inflammation, insulin resistance, and (in the case of oesophageal cancer) gastroesophageal reflux disease (GERD) may play prominent roles. In general, the main biological mechanisms linking obesity to cancer are believed to include altered sex hormone metabolism, insulin signalling, and adipokine secretion and inflammation.
They conclude: "Both early adult body weight and weight gain across adulthood were associated with the risk of most established and some potentially obesity-related cancers, with differences by cancer site, sex, and timing of weight gain. In the context of the rising prevalence of obesity and cancer in Western countries and globally, the findings highlight the importance of a life-course perspective on weight management for cancer prevention."
