When young boys gain a lot of weight at puberty, they may be increasing their risk of developing diabetes decades later, a Swedish study suggests.
Researchers examined body mass index (BMI) measurements for 36,176 men when they were 8 years old and when they were 20, then followed the men through health records from age 30 for an average of almost three decades. During this time, 1,777 men developed diabetes.
Men who were overweight as kids but not during puberty were no more likely to develop diabetes in adulthood than those who maintained a healthy weight throughout childhood, the study found.
But men who became overweight during puberty were more than four times as likely to develop diabetes before age 55 and more than twice as likely to develop diabetes after 55 than men who were never overweight as kids.
"The change in weight status through puberty conferred an independent and higher risk than simply having a high BMI through childhood," said Dr. Elif Arioglu Oral, a diabetes researcher at the University of Michigan in Ann Arbor who wasn't involved in the study.
"If the children reach puberty with increased BMI, they should be encouraged to work on decreasing the BMI as they go through puberty," Oral said by email. "Changing weight status from childhood through adulthood appeared to negate the effect of increased BMI as a child."
Globally, nearly one in five children and adolescents are overweight or obese, according to the World Health Organisation.
Children and teens are considered obese when their BMI, a ratio of weight to height, is higher than that of 95 per cent of other youth their same age and sex. They're considered overweight with a BMI in the 85th to 95th percentile range.
In the current study, researchers focused on the risk of type 2 diabetes, the most common form of the disease, which is linked to obesity and aging and happens when the body can't properly use or make enough of the hormone insulin to convert blood sugar into energy. The disease can lead to complications like blindness, kidney failure, nerve damage and amputations.
Overall, 6.2 per cent of participants were overweight at age 8 and 7.4 per cent were overweight at age 20, the study team reports in the Journal of Clinical Endocrinology & Metabolism.
About 58 per cent of those who were overweight during childhood were at a normal weight by young adulthood, the study found.
At the same time, about 64 per cent of men who were overweight as young adults had been a normal weight at age 8.
The study wasn't designed to prove whether BMI during childhood or adolescence directly impacts the development of diabetes in adulthood.
"We don't know what the mechanisms behind this association are," said senior study author Dr. Jenny Kindblom of the University of Gothenburg.
Previous research suggests that transitioning to a high BMI during puberty may be associated with the development of what's known as visceral adipose tissue, or excess fat around the midsection, Kindblom said by email. This in turn has been linked to an increased risk of diabetes.
The results of the current study offer fresh evidence that parents need to keep an eye on weight gain throughout childhood and adolescence to help kids maintain a healthy weight and minimise their risk of developing diabetes, said Dr. Mark DeBoer of the University of Virginia in Charlottesville.
"Children need to start good habits of healthier eating (eating more vegetables, less saturated fat and overall fewer calories) and regular exercise (to force their body to burn more calories)," DeBoer, who wasn't involved in the study, said by email. "Ideally, the family would do these things together."