Obesity or overweight lowers school grades in teenagers suffering from metabolic syndrome, even when they do not have a serious health complication.

Metabolic syndrome means that the person suffers from a group of risk factors that put him or her at a higher risk of developing chronic conditions like heart disease, diabetes type-2 or stroke.

"Kids who are struggling with their weight and moving toward having MetS may have lower grades, which could ultimately lead to lower professional achievement in the long run. These are run-of-the-mill, garden-variety kids, not kids that came into the hospital because they were sick," said the lead author of the study Dr. Antonio Convit, professor of psychiatry and medicine at NYU School of Medicine.

The study, published in journal Pediatrics, included more than a 100 teenagers; 49 of which had metabolic syndrome. Researchers compared learning ability of students with and without metabolic syndrome after adjusting for other factors like age, gender and cultural differences.

They found that teenagers with metabolic disorder did badly at math and language. Brain scans of these teenagers showed decreased activity in the hippocampus - region of the brain that helps in recall of new information; decreased attention span and lower mental flexibility and increased levels of cerebrospinal fluid. These differences were proportional to metabolic syndrome meaning that the more risk factors the teenager had, the more were the problems with learning.

"It is imperative that we take obesity and physical activity seriously in children. In this country, we're taking away gym class in order to give children more class time in an effort to improve school performance, but that effort may be having the exact opposite effect," said Dr. Convit.

"The take home message is that just being overweight and obese is already impacting your brain," Convit added.