Obesity can't be associated with poor academic performance at school is the emphatic conclusion of a new study.

Researchers used both statistical and genetic methods to find out if obesity was linked to children performing poorly at school. They report that no direct link was found between obesity and academic performance.

"We sought to test whether obesity 'directly' hinders performance due to bullying or health problems, or whether kids who are obese do less well because of other factors that are associated with both obesity and lower exam results, such as coming from a disadvantaged family," said  Dr. Stephanie von Hinke Kessler Scholder from the University of York.

 The researcher team analyzed data from almost 4,000 participants enrolled in the Children of the 90s Birth Cohort Study. The study includes a database of genetic material from these children. Researchers used genetic markers to see which children were naturally pre-disposed to obesity.

Childhood obesity has been linked to poor scores in math in both boys and girls. However, whether childhood obesity affects cognitive function is still controversial. Some studies say that high BMI levels negatively affect academic performance. A study published in the journal Obesity says that being overweight is not independently associated with poor academic performance in primary school children.

Researchers in the present study said that they didn't find any evidence that obesity causes poor academic performance.

"Based on a simple correlation between children's obesity as measured by their fat mass and their exam results, we found that heavier children did do slightly worse in school. But, when we used children's genetic markers to account for potentially other factors, we found no evidence that obesity causally affects exam results. So, we conclude that obesity is not a major factor affecting children's educational outcomes," explained Dr Scholder.

Researchers say that future studies must focus on obesity along with socio-economic class and educational achievements rather than just obesity.

"Clearly there are reasons why there are differences in educational outcomes, but our research shows that obesity is not one of them," said Dr Scholder.

The Centers for Disease Control and Prevention (CDC), says that 12.5 million children and teens are affected by obesity which is nearly 17 percent of all children in U.S.

Children now are getting heavier than ever. In the past few years childhood obesity has almost has tripled, the agency says.

Childhood obesity is known to bring in complications like glucose intolerance, hypertension and high cholesterol.