NEW YORK (Reuters Health) ¿ Even "chunky" kids who aren't obviously overweight have changes in their heart and blood vessel function that could increase their risk of cardiovascular disease, a new study shows.

The findings are "a wake-up call for parents, for caretakers for the community and for paediatricians," lead researcher Dr. Yanbin Dong of the Medical College of Georgia, Augusta, told Reuters Health. He and his colleagues are now following the adolescents in the current study to determine if these changes do indeed lead to worse heart health.

Dong and his team conducted the study when the term "at risk for overweight" was used to refer to a body mass index (BMI), the ratio of height to weight, that would currently be classified as "overweight'', but not obese.

While the increased risk of cardiovascular disease associated with being overweight is well known, Dong noted, it hasn't been clear whether people who fall into the "at risk" category are also at greater risk. To investigate, he and his colleagues compared several different measurements of cardiovascular function to weight status in 972 white and black twins who were an average of 17 years old.

About 17 percent of both black and white children were overweight, the researchers found, while 22.6 percent of black youths and 12.1 percent of white children were obese.

For nearly every parameter of cardiovascular health the researchers checked, from blood pressure to function of the left ventricle, the heart's main pumping chamber, the overweight white and black youth had worse scores than the healthy-weight youth, but better scores than the obese youth.