A typical boy with ADHD can appear to be in perpetual motion, but that activity doesn’t guarantee a healthy weight when he grows up. A long-term study released Monday finds that men diagnosed with attention deficit hyperactivity disorder as children are twice as likely to be overweight or obese in adulthood as those who never had the disorder.

These findings, published in Pediatrics, may be surprising to parents because drugs such as Ritalin or Adderall used to treat ADHD can suppress appetite, said Dr. F. Xavier Castellanos, the study co-author and a professor of child and adolescent psychiatry at New York University.

Robert Bukaty / AP Ritalin can suppress the appetite in children who take it for ADHD.

“It’s not uncommon for kids treated with ADHD medications to be fairly thin,” Castellanos said. Because parents often worry that thinner boys won't grow as tall, “sometimes [they] will encourage their boys to eat more.”

Instead, to help avert weight problems down the road, parents should be alert to poor eating habits. “If anything, you have to pay attention to how many times they’re having fast food, how many times they’re having fried food, whether they’re getting meals supersized," Castellanos said.

The study comes at a time when ADHD rates are rising. A new report from the Centers for Disease Control and Prevention found that ADHD is the most common mental health issue in children ages 3-17, with nearly 7 percent of kids receiving a diagnosis.

The NYU researchers followed 222 boys -- 111 with ADHD and 111 without, for an average of 33 years -- hoping to better understand the disorder's effects on the brain. The boys with ADHD, all from middle-class, white families, were diagnosed between the ages of 6 and 12.

Decades later, when some of the men returned for brain scans, many of the now 40-something adults who had ADHD as children had gained so much weight they barely fit into the fMRI machine, Castellanos said.

The researchers then asked about the body-mass index of all 222 participants, discovering that men diagnosed with ADHD as children were significantly heavier than those without the disorder. The average BMI for the ADHD participants was 30.1, compared to 27.6 among those who never had the disorder. The obesity rate among the men who’d had an ADHD diagnosis was 41.4 percent, compared to 21.6 percent among those who never had the disorder.

An adult with a BMI of 25 or higher is considered overweight, according to the Centers for Disease Control and Prevention.

Castellanos suggested the connection between obesity and an ADHD diagnosis may be explained by some of the disorder's common symptoms: lack of impulse control; difficulty paying attention to details; and poor planning skills. These symptoms could lead to problems such as unhealthy food choices and an irregular eating patterns that continue into adulthood, he said.

While the study was only of men, Castellanos suspects that the results would hold true for women as well.

The new study “shows exactly what I would have expected,” said child psychiatrist Dr. James McGough, director of the UCLA ADHD clinic. “People with ADHD have a terrible time delaying gratification. They’re very impulsive and they don’t think about consequences. Their problems with organization may make it more difficult to stay on a regular eating schedule which leaves them more likely to binge eat.”

Obesity expert Dana Rofey says “sneak eating and aberrant eating patterns” are common among many of her young, male patients with the disorder.

“Once they start eating, they don’t stop,” said Rofey, an assistant professor of pediatric psychiatry and psychology at the University of Pittsburgh Medical Center and weight management director at the Children’s Hospital of Pittsburgh.

Rofey hopes the study will prompt parents to help their sons develop healthful eating habits -- before they become a problem.

“That may mean tracking food intake or using a pedometer to keep track of activity, she said. “You want to encourage your child to do more outside with their friends, instead of spending hours texting or looking up their friends on Facebook.”

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