While we often try our best not to live in the past, our biology often has other ideas. Researchers found that men who were overweight in their youth had a significantly higher risk of developing 17 different cancers. In two new studies, scientists from the University of Gothenburg examined the body mass index (BMI) of 1,489,115 men who were conscripted into the Swedish military between 1968 and 2005, regardless of their aerobic fitness levels. During the follow-up period, approximately 84,621 people were diagnosed with some form of cancer.
They found that those with a high body mass index when they enlisted had a higher risk of developing cancers of the lung, head and neck, brain, thyroid, esophagus, stomach, pancreas, liver, colon, rectum, kidney and bladder, as well as malignant melanoma, leukemia, myeloma and lymphoma (Hodgkin's and non-Hodgkin's).
Aron Onerup, first author of the study from the University of Gothenburg, said: "Being overweight and obese at a young age appears to increase the risk of cancer, and we found that unhealthy weight is associated with cancer in almost all organs. Given the worrying trends in childhood and adolescent obesity, this study reinforces the need to deploy strong resources to reverse this trend."
Interestingly, the incidence of several cancers is already higher in men with a body mass index of 20-22.4 [within the "normal" range (18.5-24.9)]. These cancers include head and neck, esophageal, stomach, pancreatic, liver and kidney cancers, as well as malignant melanoma and non-Hodgkin lymphoma.
"This suggests that current definitions of normal weight may apply mainly to older adults, while optimal weight for younger adults may be in a lower range," said senior author Maria Åberg, professor of family medicine at the University of Gothenburg. "Our research group reached similar conclusions regarding body mass index in early adulthood and cardiovascular disease later in life."
While it's generally accepted that body mass index doesn't provide a complete picture of a person's weight or health, research has found significant links between cancer and these measures.
People with a high body mass index at school have three to four times greater risk of developing abdominal cancers later in life, including esophageal, stomach and kidney cancers. Currently, weight problems in youth are estimated to account for 15%-25% of these cancer cases in Sweden.
Researchers predict that in 30 years, weight-related cancer rates will have risen significantly. For example, they predict that 32% of stomach cancer cases and 37% of esophageal cancer cases will be related to historical weight problems.
Additionally, analysis of the data showed that overweight or obese men were two to three times more likely to die within five years of a diagnosis of skin cancer, Hodgkin's lymphoma, thyroid, bladder and prostate cancer, and twice as likely to die from head and neck, rectal and kidney cancers.
The study linked high body mass index to a greater risk of developing 18 different cancers in more than 2.6 million Spanish adults.
Meanwhile, the Centers for Disease Control and Prevention (CDC) currently says weight plays a role in the incidence of 13 different cancers. However, the Centers for Disease Control and Prevention also points out that cancer is not an inevitable result of obesity at any stage of life, and the risk can be reduced through better lifestyle choices or medical intervention. It also emphasizes the importance of vigilant health checks and monitoring for early signs of disease. The Swedish researchers also note that the obesity epidemic is sure to put increasing pressure on the healthcare system as people age and become more susceptible to these cancers.
Two papers from the study were published in the journals Obesity and Cancer Medicine.