TUESDAY, Jan. 17 (HealthDay News) -- Retired National Football League players who pack on the pounds may not be as sharp later in life as their counterparts who maintain a healthy weight, a new study suggests.

Previous research has found that pro football players are already at risk for cognitive problems, including dementia, due to repeated head trauma during their on-the-field years.

The new study, published in the Jan. 17 online issue of Translational Psychiatry, evaluates how their weight may affect brain health.

"The overweight group had significantly less activity and mental acuity," said study co-author Dr. Daniel Amen, medical director of Amen Clinics, in Newport Beach, Calif.

Amen and his colleagues recruited former NFL players between the ages of 25 and 82 for their study. Most of the study participants were middle-aged. Each had been on an active NFL roster for at least three years. To learn more about the relationship between their weight and brain health, the scientists compared 38 healthy-weight and 38 overweight players.

The participants met with a doctor and answered questions about their health history, and their weight and waistlines were measured. They were also given a series of cognitive tests measuring a range of brain functions, including memory, how fast they processed material, attention and reasoning.

Each participant also underwent brain scans -- single-photon emission computed tomography (SPECT) -- to measure blood flow to the brain. Amen said heavier athletes were more likely to have poorer blood flow in the temporal and prefrontal cortex regions, which are areas of the brain involving attention, reasoning and executive function. Poorer results on cognitive tests corresponded to poorer blood flow in the higher-weight patients, too, he said.

Amen said he was also concerned by the amount of depression reported by the athletes. "The levels of depression, dementia and obesity really shocked us and they all worked together," he said.

Dr. Ausim Azizi, chair of the department of neurology at Temple School of Medicine, in Philadelphia, called the new research a well-designed study. But he wonders if weight gain was the cause of increased cognitive decline, or if head injuries incurred during the players' careers led to poorer decision-making about diet and health, which, in turn, led to weight increase.

"Was the weight gain a cause or an effect of brain injury?" Azizi asked.

Either way, being overweight is concerning, he said, because it can lead to or exacerbate other health problems, including high blood pressure and type 2 diabetes, both linked to cognitive decline.

"Being overweight is an index of other diseases," Azizi said.

Neuropsychologist Summer Ott, co-director of the Methodist Concussion Center in Houston, said that while the study suggests weight gain may be linked to cognitive problems in later life, she believes many factors are at play in the retired athletes and they need to be addressed.

"We don't want to put all our eggs in one basket and say cognitive decline is all due to head injury and obesity," said Ott, who has worked with athletes.

She said a multifaceted approach to brain health -- including management of head injury early in a player's career and then access to health resources after retirement -- would benefit the players.

"When they quit their sport, a weight-management program coupled with psychotherapy and resilience training would help," Ott said. "What I believe is happening, especially with those who retire early, is that a significant change in their identity occurs. It's sort of like those in the military. The players are coming back and reintegrating into a whole new environment. They aren't with their guys anymore. They've put all emphasis into being a professional athlete and haven't really prepared for the world after athletics."

While the new study only reported on weight, Amen believes a support system that helps retired players stay slim would go a long way toward their physical and mental health. "I think of depression, obesity and dementia as different expressions of the same lifestyle," he said.

More information

For more on the health risks of obesity, visit the office of the U.S. Surgeon General.