19 February 2013

Medicos mull possible link between obesity and ADHD

by Will Parker

A new University of Illinois study has established a possible link between high-fat diets and childhood cognitive conditions such as attention deficit hyperactivity disorder (ADHD) and memory-dependent learning disabilities.

The research, published in Psychoneuroendocrinology, found that altered dopamine signaling (previously associated with anxiety behaviors in children) in the brain is common to both ADHD and the overweight state.

Working with mice, researcher Gregory Freund examined the short-term effects of a high-fat (60 percent of calories from fat) versus a low-fat (10 percent of calories from fat) diet on the behavior of two groups of four-week-old mice. A typical Western diet contains around 40 percent fat. "After only one week of the high-fat diet, even before we were able to see any weight gain, the behavior of the mice in the first group began to change," he said.

Evidence of anxiety included increased burrowing and wheel running as well a reluctance to explore open spaces. Freund said the mice also developed learning and memory deficits and impaired object recognition, but switching from a high-fat to a low-fat diet restored memory in one week.

In mice that continued on the high-fat diet, impaired object recognition remained three weeks after the onset of symptoms. But Freund knows from other studies that brain biochemistry normalizes after 10 weeks as the body appears to compensate for the diet. At that point, brain dopamine has returned to normal, and the mice have become obese and developed diabetes.

"Although the mice grow out of these anxious behaviors and learning deficiencies, the study suggests to me that a high-fat diet could trigger anxiety and memory disorders in a child who is genetically or environmentally susceptible to them," he said.

Freund says the study provides evidence that a high-fat diet initiates chemical responses that are similar to the ones seen in addiction, with dopamine, the chemical important to pleasurable experiences, increasing in the brain. "We found that a high-fat diet rapidly affected dopamine metabolism in the brains of juvenile mice, triggering anxious behaviors and learning deficiencies. Interestingly, when methylphenidate [Ritalin] was administered, the learning and memory problems went away," he concluded.

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Source: University of Illinois College of Agricultural, Consumer and Environmental Sciences