High BMI during childhood and puberty has been linked to higher risk of cancer in men later in life, according to a new study led by Jimmy Celind, researcher at Sahlgrenska Academy’s Institute of Medicine, Sweden.
“Overweight in childhood followed by normal weight in young adulthood thus resulted in a persistently increased risk of adult obesity-related cancer, which this study is the first to show,” he said.
“We were somewhat surprised by this, and that the risk associated with childhood overweight was persistent even in the group that lost their overweight by young adulthood,” Celind told Inside Precision Oncology.
These results were recently published in the journal Cancer Communications, and are based on the BMI Epidemiology Study Gothenburg, a population-based cohort including BMI during development and diagnostic data from high-quality Swedish registers on 36,565 men born in 1945–61.
The scientists analyzed BMI of the included individuals at the age of 8 years and again at 20 and followed up their cancer diagnoses from age 20 and approximately 40 years thereafter. This long follow-up period was crucial to the study since most cases of obesity-related cancer occur in upper middle age.
The study shows that the group of boys overweight at age 8 had an increased risk of obesity-related cancer in adulthood. This applied particularly to those whose weight remained elevated at age 20. However, an increased risk also remained when BMI had become normal by the of 20. The threshold for overweight used was the CDC cutoff — a BMI >17.9 for boys 8 years old and >25 for those 20 years old.
“Alarmingly, a near 40 percent excess relative risk remained even for the group of boys who were overweight at age 8 but had a normal weight at age 20, compared to the group with normal weight at both ages” says Celind, who is also a pediatrician at the Queen Silvia Children’s Hospital.
Celind told Inside Precision Oncology, that, “There are several mechanistic theories as to why obesity contributes to cancer risk. Since our study was not designed to answer mechanistic questions, these theories come from other studies. They include increased risk due to chronic systemic inflammation often associated with obesity, higher levels of glucose and insulin in the blood, and aberrations of fat-specific proteins (called adipokines), to mention a few.”
He added that, “When it comes to mechanistic theories as to how overweight in childhood could be associated with increased risk of cancer in late adulthood, i.e., many decades later, they include genetic and metabolic programming during sensitive phases of development.”
Obesity-related cancers include a significant group of tumor diseases, many of which are on the rise in industrialized countries. They include cancer of the mouth, liver, gallbladder, pancreas, colon, and thyroid, skin (malignant melanoma) and blood.
The authors of the study emphasize that the results are not applicable to individual risk. “The increased risk for the individual over a life course is minor. However, in a population like the Swedish, where one in five children are overweight, these findings point towards significant negative impact on future populational health.”
“The results show that preventive measures against obesity-related cancer should start early in childhood. If decision makers responsible for public health at country or even global level are serious about every child´s right to a healthy start in life, they need to step up the actions taken in early years,” Celind says.
