Being overweight or obese counts among the risk factors associated with many chronic diseases, but one study now reveals that they may play a role in the development of as many as 17 types of cancer, starting as soon as the end of adolescence.
Carried out exclusively on men, this research underlines the importance of taking new action to combat sedentary lifestyles at a time when obesity is on the rise worldwide.
The study by researchers at Sweden’s University of Gothenburg highlights the role of obesity, and more generally of a high body mass index (BMI), on health, and in particular on the risk of cancer.
The analysis involved no fewer than 1.4 million men who took the conscription examination between 1968 and 2005, when they were aged between 16 and 25, nearly 80,000 of whom went on to develop cancer during an average follow-up period of 31 years.
Published in the journal Obesity, this research suggests that a high BMI at age 18 – late adolescence – is linked to an increased risk of several types of cancer in adulthood, more so than having poor fitness at the same age.
“Overweight and obesity at a young age seems to increase the risk of developing cancer, and we see links between unhealthy weight and cancer in almost every organ,” said first author Aron Onerup from the University of Gothenburg.
‘Given the alarming trend of obesity in adolescence, this study reinforces the need to deploy strong resources to reverse this trend.”
In the course of their investigations, researchers observed a higher risk of cancer of the lung, head, neck, brain, thyroid, oesophagus, stomach, pancreas, liver, colon, rectum, kidney and bladder, as well as melanoma, leukaemia, myeloma and lymphoma in participants with a high BMI at the average age of 18.
A BMI greater than 25 was considered high.
The researchers point out that this association was even stronger for cancers of the oesophagus, stomach and kidney, reporting a risk three to four times higher for men who were obese at age 18.
It should be noted, however, that a BMI considered normal – that is, between 20 and 22.4 – was nevertheless associated with an elevated risk of cancers of the head, neck, oesophagus, stomach, pancreas, liver, kidney, melanoma and non-Hodgkin’s lymphoma.
This astonishing finding may suggest that “the current definition of normal weight may be applicable primarily for older adults, while an optimal weight as a young adult is likely to be in a lower range”, said senior author Maria Åberg.
“In 30 years, the researchers expect an increase in the proportion of cancer cases linked to youth overweight and obesity, calculated based on overweight and obesity in today’s 18-year-old men in Sweden. For cancer of the stomach, the proportion rises to 32%, and for cancer of the oesophagus to 37%.
“Based on the current prevalence of youth overweight and obesity in the United States, more than one in two cases of these two cancers could be linked to high BMI in the late teenage years in 30 years,” the research concludes.