Predicting an overweight child's risk of diabetes and heart disease may be as simple as measuring the size of his or her wrist, according to new research published by the American Heart Association. In the study, published in the latest addition of the journal Circulation, wrist size was linked to insulin resistance, a precursor for type 2 diabetes, in overweight kids and teens.
"This is the first evidence that wrist circumference is highly correlated to evidence of insulin resistance," Dr. Raffaella Buzzetti, senior study author and professor in the Department of Clinical Sciences at Sapienza University of Rome, Italy, said in a statement. "Wrist circumference is easily measured and if our work is confirmed by future studies, wrist circumference could someday be used to predict insulin resistance and cardiovascular disease risk."
Though measuring body fat is usually a reliable predictor of insulin resistance and heart disease risk in adults, this is not always the case for kids because their bodies grow and change so rapidly during puberty. Typically, doctors will measure a teen's BMI (body mass index) by comparing height and weight. This may be a misleading gauge, however, especially for athletes who may have a high percentage of muscle, which weighs more than fat.
In the study, researchers analyzed how wrist size and BMI correlated with levels of insulin resistance. While BMI only accounted for 1 percent of variation in insulin resistance, the wrist measurement accounted for between 12 and 17 percent.
Insulin resistance occurs when the body has difficulty using the insulin it makes to break down blood sugar. Excess body fat is linked to developing insulin resistance, and insulin resistance has been identified as a major risk factor for developing cardiovascular disease and type 2 diabetes later in life.
Surprisingly, researchers found that it wasn't necessarily a fatter wrist that correlated with higher heart disease risk, just a larger one. Because higher insulin levels in kids can contribute to increased bone production, larger wrist bones may be a marker of insulin resistance, which in turn is a predictor of future heart disease.
"It's surprising that bone size correlated better [to insulin resistance] than body mass index," says Dr. Robert Gensure, endocrine specialist and pediatric bone density specialist at Montefiore Medical Center. "Insulin is a growth factor and it promotes growth in many tissues, including bone."
This means that some kids and teens who are overweight are actually becoming bigger-boned in response to the extra insulin their bodies are producing. Buzzetti's research is picking up on this change and using those bigger bones as an indicator of the higher levels of insulin that put kids at risk for future heart disease and diabetes.