Weight loss may limit diabetes-related brain changes

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Losing weight may help people with diabetes limit damaging changes to the brain that can result from the disease, a U.S. study suggests.

Researchers followed a group of diabetics for more than a decade, offering 164 of them intensive counseling with diet and exercise support designed to help them shed at least 7 percent of their weight and keep it off. Another 155 diabetics received only a standard disease education program.

The counseling group lost more weight and achieved greater gains in cardiorespiratory fitness than their peers in the control group.

And, in a sign that weight loss might protect against diabetes-related brain damage, the control group had smaller volumes of gray matter and more white matter disease by the end of the study. Smaller volumes of brain tissue and the presence of white matter disease are linked to cognitive decline.

"If individuals with diabetes change their behavior in mid-life to lose weight and increase physical activity, this can lead to long-term benefits in brain health later in life," said lead study author Mark Espeland, a public health researcher at Wake Forest School of Medicine in Winston-Salem, North Carolina.

Globally, about one in nine adults have diabetes, and the disease will be the seventh leading cause of death by 2030, according to the World Health Organization.

Most of these people have type 2, or adult-onset, diabetes. Their bodies can't properly use or make enough of the hormone insulin to convert blood sugar into energy.

The brain consumes about 20 percent of the energy the body uses, and the main source of that energy is blood sugar, Espeland said. Diabetes makes blood sugar a less reliable energy source, which can compromise brain function and lead to cognitive decline over time.

To see if intensive lifestyle changes might counter the effect of diabetes on the brain, Espeland and colleagues offered one group of study participants intensive counseling, encouraged calorie-restricted diets with limited amounts of fats and proteins and set exercise goals of at least 175 minutes a week of moderate activity, which amounts to brisk walking.

The counseling group participants initially had weekly sessions, followed by monthly meetings for an extended period of time. By contrast, the other group receiving just standard care was invited to attend group classes a few times a year.

Over the first year, the intensive counseling group lost about 12 percent of their weight on average, compared with less than 1 percent in the control group. Cardiorespiratory fitness, or the ability to supply oxygen to the muscles during exercise, improved about 26 percent for the counseling group over the first year, compared with 7 percent for the others.

While the counseling group gave back some of these initial gains over the course of the 10-year study, they still did better than the other diabetics over the long run.

Total brain volume was similar between the two groups. But the average volume of so-called white matter hyperintensities - concentrations of white matter that represent damaged areas, which can happen with age and be worsened by diabetes - was 28 percent lower for the counseling group than the other participants.

Another sign of deterioration, the average volume of fluid-filled cavities called ventricles, was 9 percent lower for the counseling group than for the others.

Overall, both groups had similar cognitive function at the end of the study, although the counseling group performed better on tests of attention and processing speed.

One limitation is that researchers didn't look at other factors that might lead to better diabetes control and potentially protect the brain, such as blood pressure, sleep apnea, depression, medication use and inflammation, the authors note in the journal Diabetes Care.

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Still, weight loss and other lifestyle changes reduce high glucose levels that are toxic to the brain, Dr. Caterina Rosano, a researcher at the University of Pittsburgh who wasn't involved in the study, said by email.

"The results from this and other studies suggest that a healthy lifestyle with appropriate diet, exercise and cognitive stimulation may help preserve brain function and structure in diabetics over pharmacological treatment alone," Dr. Joe Verghese, director of the Montefiore-Einstein Center for the Aging Brain said by email.