Can Diet and Exercise Prevent Loss of Brain Cells in Type 2 Diabetes?

Brain and White Matter Hyperintensity Volumes After 10 Years of Random Assignment to Lifestyle Intervention (Diabetes Care 2016;39:764–771. doi: 10.2337/dc15-2230)

What is the problem and what is known about it so far?

Adults with type 2 diabetes are more likely to have something called brain atrophy, a loss of cells and the connections between cells in the brain. Over time, their brains can shrink and have too much "white matter." This change in brain structure is a big concern—gray matter in the brain contains brain cells, so less gray matter and more white matter would be a sign of brain cell death. People with diabetes are also more likely to have diseases of the blood flow in the brain (cerebrovascular disease), which can cause conditions like stroke. Brain atrophy and cerebrovascular disease may lead to cognitive impairment in individuals with diabetes, meaning that for individuals with diabetes it is harder to process or acquire knowledge. It can also lead to dementia, a decline in thinking skills and memory. It is estimated that 1 of every 15 cases of dementia is due to diabetes.

Why did the researchers do this particular study?

Weight loss through diet and exercise in people with type 2 diabetes could have positive effects on brain structure and protect the brain over time. This has not been proven, but researchers believe it is possible. This study was the first description of how lifestyle interventions such as diet and exercise affect brain structure over a long period of time.

Who was studied?

Overweight and obese adults with type 2 diabetes, ages 45–76 years, were followed for 10 years. One group received intensive behavioral and lifestyle intervention including individual or group counseling. The goal of this group was to lose at least 7% of weight through diet and exercise in the first year and then keep the weight off through the remainder of the study. They were assigned a daily calorie goal (1,200–1,800 based on starting weight) and a physical activity goal of 175 minutes or more of physical activity per week (at the level of intensity of brisk walking). Individuals in this group were weighed, encouraged, and seen regularly (3–6 times a month). The other group, the "control" group, received traditional diabetes support and education only three times a year through group sessions on diet, physical activity, and social support.

How was the study done?

To study brain structure, magnetic resonance imaging (MRI) was done to look at participants' brains and see if there were any differences in brain size (volume) or amount of white matter between the groups. Cognitive function (attention, concentration, memory, etc.) was also evaluated through various surveys and tests and compared between the groups.

What did the researchers find?

The group that received intensive intervention exercised more and lost more weight than those in the control group. The researchers looked at total brain volume and at the amount of white matter in both groups. Although total brain volume was almost the same between the groups, the ventricles (the spaces or cavities within the brain) were larger in individuals in the intensive intervention group, indicating less brain shrinkage. This group also had less white matter overall, indicating less brain cell death. The cognitive function test results were about the same for both groups.

What were the limitations of the study?

Because participants volunteered for the intense lifestyle intervention, they may have been healthier than other overweight or obese adults with diabetes. Because those who were not overweight or those without diabetes were not studied, there were no "baseline" brain structure measurements for comparison. Also, it is unknown whether factors such as blood pressure or medications could have had an effect.

What are the implications of the study?

According to the findings of this study, long-term weight loss intervention for those with type 2 diabetes may delay increases in cerebrovascular disease and brain atrophy, ultimately reducing the likelihood of stroke and dementia. If true, this would mean that behavioral intervention is even more important for people with diabetes and could have great public health significance. It is unknown whether the positive effects on brain structure could result in better brain function.

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