Most people have heard or read about calorie restriction being a technique for living longer. This is the first I have heard of it affecting cognition.
Several studies have reported that actively cutting down on calories – not simply “watching your weight” – might also be an effective strategy against cognitive decline, according to the Tufts University Health & Nutrition Letter.
One German study found a connection between a restricted-calorie diet and improved memory among participants divided into three groups: One aimed to reduce calorie intake by 30 percent, mostly by eating smaller portions; a second group kept calories the same while increasing intake of healthy fats by 20 percent; and a third, the control group, made no dietary changes.
At the end of three months, the calorie cutting group scored an average of 20 percent better in tests of memory performance; the other groups showed no change. Researchers theorized that the calorie-cutters, who lost four to seven pounds, might experience brain benefits from decreased insulin and inflammation.
In another study, researchers compared the calorie intakes of older people suffering mild cognitive impairment (MCI) with normal control subjects. Those consuming the most calories—more than 2,143 per day—were almost twice as likely to have MCI than participants eating the least, fewer than 1,526 daily calories.
The higher the amount of calories consumed each day, the higher the risk of MCI. The results were the same after adjusting for history of stroke, diabetes, amount of education, and other factors that can affect risk of memory loss.
Blood Sugar Risks and Calorie Restriction
Being overweight or obese also affects your blood sugar levels, increasing the risk of diabetes. Chronically high blood-glucose (sugar) levels, whether from insulin resistance, prediabetes, or type 2 diabetes, seem in turn to affect the brain.
One study linked higher blood glucose levels with a 40 percent greater risk of developing dementia. Blood glucose levels of people with diabetes who developed dementia over seven years averaged 190 mg/dl, compared to 160 mg/dl in those who did not develop dementia.
(Normal fasting glucose levels are below 100 mg/dl and levels above 126 mg/dl are considered diabetes.)
People whose blood glucose is higher than normal but not high enough to meet the criteria for diabetes are also at greater risk.
That same study found that people with the highest levels—but short of diabetes—were 20 percent more likely to develop dementia than those with normal blood-glucose levels. Among non-diabetic participants, those who developed dementia had blood-sugar levels averaging 115 mg/dl, compared with 109 mg/dl for those who did not develop dementia.