Although the cause of these cognitive impairments is still unknown, University of Florida (UF) researchers suspect the metabolic disturbances obesity causes could be taking a toll on young brains, which are still developing and not fully protected.

Researchers compared 18 children and adults with early-onset morbid obesity, which means they weighed at least 150 percent of their ideal body weight before they were 4, with 19 children and adults with Prader-Willi syndrome, and with 24 of their normal-weight siblings. Researchers chose lean siblings as a control group "because they share a socioeconomic group and genetic background," said Daniel J. Driscoll, M.D., Ph.D., a UF professor of pediatrics and molecular genetics and microbiology in the College of Medicine.

The links between cognitive impairments and Prader-Willi syndrome, a genetic disorder that causes people to eat nonstop and become morbidly obese at a very young age if not supervised, are well-established. But researchers were surprised to find that children and adults who had become obese as toddlers for no known genetic reason fared almost as poorly on IQ and achievement tests as Prader-Willi patients. Prader-Willi patients had an average IQ of 63 and patients with early-onset morbid obesity had an average of 78. The control group of siblings had an average IQ of 106, which falls within the range of what is considered normal intelligence.

While performing head Magnetic Resonance Imaging scans of subjects, researchers also discovered white-matter lesions on the brains of many of the Prader-Willi and early-onset morbidly obese patients. White-matter lesions are typically found on the brains of adults who have developed Alzheimer's disease or in children with untreated phenylketonuria, the researchers wrote.

These lesions could be affecting food-seeking centres of the brain, causing the children to feel hungrier. But they are most likely a result of metabolic changes that damage the young, developing brain, Discroll said.; Source: University of Florida