By Janet Raloff, Science News
Previous research has linked being overweight in childhood with a higher risk of these chronic diseases in adulthood, but the new study is the first to identify the ages between 2 and 6 years as the most important in predicting later risk of metabolic syndrome, says the study's lead author, physician Marlou de Kroon of VU University Medical Center in Amsterdam. The condition is associated with increased risk of type 2 diabetes and cardiovascular diseases.
The new work "is very interesting," says cardiologist Gerald Berenson, because it reveals the earliest and most critical age for predicting adult weight problems and risk of serious chronic disease. Berenson, who was not involved in the new study, is director of Tulane University's Center for Cardiovascular Health in New Orleans.
In the face of a growing epidemic of childhood obesity, these data are very disturbing, Berenson says. People often disregard children's weight problems, rationalizing "that kids will grow out of it during puberty," he says. But the new study shows that the kids may not—and if they don't, big problems could ensue.
To explore the relationship between early weight gain and later disease risk, researchers repeatedly measured the height and weight of 642 Dutch children born between 1977 and 1986 in Terneuzen, the Netherlands. From these measurements, scientists calculated the youngsters' body-mass index—or BMI, which is a measure of heaviness that accounts for height—at least once a year from birth through age 18. Then they plotted how BMI changed over time. Later, as young adults aged 18 to 28, the participants returned for follow-up measurements of waist circumference, fat under the skin and blood tests.
Increasing BMI between the ages of 2 and 6 more than tripled the risk that a young adult would exhibit signs of metabolic syndrome, de Kroon and her colleagues report in a paper published online November 12 in PLoS One. BMI increases between the ages of 10 and 18 also posed a substantial—albeit lower—link to metabolic syndrome. The analyses indicated less than a 5 percent likelihood these associations were due to chance.
Metabolic syndrome is a constellation of symptoms that occur together and tend to include elevated blood pressure, elevated triglycerides (fat in the blood), elevated C-reactive protein (a marker of chronic, systemic inflammation) and diminished high density lipoprotein cholesterol, also known as good cholesterol. Until recently, metabolic syndrome was rarely observed before middle age.
Earlier this year, de Kroon's team also reported that BMI gains between the ages of 2 and 6 were most predictive that a young adult would be overweight.
Although increasing BMI was a strong risk factor for adult disease, being a big baby with an unvarying but high BMI was also associated with higher risk of metabolic syndrome in adulthood, de Kroon says. Weighing too much appears to be bad for adult health, whether a child starts big or merely gets that way during childhood. Moreover, she points out, "if a very thin child is becoming heavier, it may still have a very high risk [of adult disease] even if it never seems too fat." So even parents of slim kids should watch that children don't exceed the normal growth curve, she says.
As director of the Bogalusa Heart Study in Louisiana, Berenson and his colleagues tracked weight changes in children from 8 to 17 and showed that a high BMI in childhood was a strong predictor that metabolic syndrome and prediabetes would emerge in adulthood.
Are the new data strong enough for pediatricians to begin cautioning all parents to avoid weight gain in children? "Oh gosh, you know they are," Berenson says. But, he notes, "We've been riding like the dickens to get even cardiologists interested in primordial prevention"—taking action to prevent the development of heart and diabetes risks in apparently healthy individuals. And that should definitely start with addressing the growing number of pudgy children, he says.