Overweight teens face possible loss of brain power

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Here's some food for thought: A new study says that piling on the pounds can affect the brain power of adolescents.

Metabolic syndrome -- a group of risk factors that has been studied in overweight and obese adults -- may not only hurt the neurocognitive abilities and school performance of overweight teenagers, but also cause physical changes in the brain, according to the study, which is being published in the journal Pediatrics this month.

Metabolic syndrome is defined as having three or more health problems that raise the risk of serious diseases. Those health problems include pre-diabetic insulin resistance, high blood pressure, low levels of "good" (HDL) cholesterol, high triglycerides and abdominal obesity.

The New York University study is believed to be the first to demonstrate brain abnormalities among overweight adolescents with the syndrome, said researchers, who conducted brain imaging and various tests of thinking skills in two groups of participants -- 49 adolescents with metabolic syndrome and 62 without it.

Previously, impaired brain function in obese adults was thought to be linked to vascular disease and the cumulative effect of years of poor metabolism, but this study found that the cognitive performance of overweight children was affected even after a relatively short period of time.

The study found lower spelling and arithmetic scores, along with lower mental flexibility and measures of attention for overweight children with the syndrome.

"The take-home message here is that the kids with metabolic syndrome took longer to do tasks, could not read as well and had poorer math scores," said Antonio Convit, the study's lead researcher. "These findings indicate that these kids do not perform well on things that are very relevant to school performance."

With metabolic syndrome, the brain has trouble efficiently processing its main source of energy, glucose, said Dr. Convit, professor of psychiatry and medicine at NYU School of Medicine and a member of the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, N.Y.

If a diabetic or someone with marked insulin resistance plunges his hand in a bucket of cold water, "we know that it takes longer for their hand to warm up afterward, because the capillaries don't work very well," said Dr. Convit. The same is true for people with metabolic syndrome, who are not yet diabetic but who show resistance to insulin, a hormone that controls blood sugar.

In overweight people with this condition, "The transporters that get the glucose from the blood into the brain are working at full throttle all the time, as fast as they can. The only way to get more juice is to relax the capillaries to allow more glucose to be transported" into the brain, but that doesn't happen.

The numbers of children diagnosed with the metabolic syndrome have paralleled the rise in childhood obesity, added Dr. Convit, noting that the study controlled for age, ethnicity, socioeconomic status, school grade and gender, addressing cultural differences in diet and access to quality health care.

This wasn't a case of comparing fat vs. thin, either.

In the group without metabolic syndrome, 40 percent were overweight or obese. They may have been free of the syndrome either because of genetics or because they exercised regularly and were, therefore, more healthy.

The group with metabolic syndrome had a significantly larger waist circumference and body mass index, along with other health issues, including high blood pressure, higher levels of bad cholesterol and insulin resistance. Neither group differed significantly in sleep apnea or depression, but the researchers decided to err on the side of caution and control for those symptoms -- and found the results to be largely unchanged.

Brain imaging tests showed differences in brain structure and volume, along with a shrunken hippocampus, which controls learning and recall of new information, along with poorer connections among different parts of the brain.

However, the study noted, 18 of the 111 participants did not have MRI data -- because they could not be accommodated by the scanner due to their large body size.

The NYU study may be pioneering, but there are numerous other, smaller studies under way looking at child obesity and metabolic syndrome. At Children's Hospital of Pittsburgh of UPMC, Dana Rofey is in the process of recruiting participants for a small pilot study looking at different degrees of insulin resistance, using a series of measures that test how people think.

"This area of research has huge implications," said Ms. Rofey, an assistant professor at the University of Pittsburgh School of Medicine. "The research on metabolic syndrome in adults is fairly well established in medical literature, and we're just starting to learn more about how being overweight affects children in school." She noted that when she sees overweight children in her work, she urges their parents to have them undergo cognitive testing in their schools.

Michael Franzen, a psychologist at Allegheny General Hospital, said the study could be one more powerful motivator in getting families to work together to be healthy.

"It just underlines the importance of intervening with kids to make changes to improve their health," said Mr. Franzen. He said AGH's pediatricians refer overweight patients and their families to KidShape, a weight management program for youths between 6 and 14 years old. Registered dietitians and mental health professionals meet with families once a week to learn about good nutrition, behavior modification, physical activity and other ways to change poor eating habits.

It sometimes takes some persuading, said Tatanisha Smith, a pediatrician at AGH. About 75 percent of her patients are enrolled in some kind of medical assistance program, with 40 percent of them "overweight/obese" -- defined as being over the 85th percentile of weight, while obesity is defined as being above the 95th percentile, she said.

Anecdotally, Dr. Smith hears numerous stories from parents about their overweight children having problems focusing in school, along with a constellation of other problems.

Whether blood tests show some kind of insulin resistance, or not, when Dr. Smith sits down and talks with the parents about the role their child's weight plays in school performance, "sometimes I definitely get a little pushback. They don't foresee weight gain as a problem. Perhaps it's a cultural issue for them, but I work to try to break down those cultural barriers and make them see that obesity is more than just the weight alone; it can cause far-reaching health problems other than just being heavy."

It's small changes that make the largest difference, Dr. Smith noted. "A lot of these children will tell you they drink two liters of Pepsi in two days, so I tell them to make a little change -- for every 12-ounce can of soda, follow it with the same amount of water. And when I ask about how often they eat out at fast-food places, they tell me five out of every seven days. If we can bring that down to just three days, we'll see benefits."


Mackenzie Carpenter: mcarpenter@post-gazette.com or 412-263-1949.


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