A new study, published in The Journal of Clinical Endocrinology and Metabolism, has found that overweight people with type 2 diabetes can improve their cognitive or brain function by controlling their blood sugar levels.

However, the study found that losing weight, especially for those who are obese and diabetics, and increasing physical activity produced mixed findings.

Dr. Owen Carmichael of Pennington Biomedical Research Center, Louisiana, said, “It’s important to properly control your blood sugar to avoid the bad brain effects of your diabetes.”

“Don’t think you can simply let yourself get all the way to the obese range, lose some of the weight, and everything in the brain is fine. The brain might have already turned a corner that it can’t turn back from,” he added.

The new study examined around 1,100 participants in the Look AHEAD (Action for Health in Diabetes) study.

They were divided into two groups. One group was invited to three sessions each year that focused on a healthy diet, physical activity, and social support, while the other group had a change in their diet and physical activity via a program that helped them lose more than 7 percent of their body weight in a year and maintain that weight loss.

The study researchers gave cognitive tests, such as tests of thinking, learning, and remembering, to participants from 8 to 13 years after they started the study.

The team found that people who had greater improvements in blood sugar levels, physical activity, and weight loss had improved cognitive test scores. However, losing more weight and exercising did not raise cognitive test scores.

Dr. Carmichael explained, “Every little improvement in blood sugar control was associated with a little better cognition. Lowering your blood sugar from the diabetes range to prediabetes helped as much as dropping from prediabetes levels to the healthy range.”

The researchers found that people who lost more weight had improved executive function skills – such as “short-term memory, planning, impulse control, attention.” Also, they had an improved ability to switch between tasks. However, their verbal learning and overall memory declined.

“The results were worse for people who had obesity at the beginning of the study. That’s a ‘too little, too late’ type of message,” Dr. Carmichael noted. “People with diabetes who let their obesity go too far, for too long may be past the point of no return, cognition-wise.” The study also found that increasing physical activity generated more benefits for overweight people than obese people.