Insulin resistance and poor blood glucose control – defining characteristics of type 2 diabetes – drive changes associated with brain aging and cognitive decline. A growing body of evidence suggests that dementia is the manifestation of insulin resistance and altered metabolism in the brain. A recent study suggests that dietary patterns that promote ketosis improve brain metabolism and function.
Ketosis is a metabolic state that results in the body’s production and use of ketones (byproducts of fatty acid metabolism). It occurs under conditions of fasting, starvation, and low carbohydrate intake. Ketones induce physiological and metabolic responses to promote brain health.
The study had multiple components. First, the authors of the study investigated the time course of human brain aging. Using functional MRI (fMRI) data from more than 900 people between the ages of 18 and 88 years, they determined that neural network stability is a biomarker of brain aging, and the loss of network stability manifests as early as the fifth decade of life (average age, 47 years). They found that the greatest changes in the brain occur around the age of 60 years.
Then they performed fMRI scans on 12 young adults (average age, 28 years) to assess how different energy sources – glucose versus ketones – alter brain function. Each participant underwent three scans under different dietary conditions: a normal diet without fasting, a normal diet with overnight fasting, or a ketogenic diet for one week. They performed fMRI scans on 30 young adults (average age 29 years) 30 minutes after they took an oral bolus of either glucose or ketones or after following their normal diet with overnight fasting. The authors of the study measured the participants' blood glucose and ketone levels before and after each of the scans.
The fMRI scans revealed that ketones increased overall brain activity and stabilized functional networks, but glucose had the opposite effect, regardless of whether the ketones were produced endogenously or supplied from exogenous sources. These findings suggest that dietary interventions that increase ketone production may be useful in mitigating the harmful effects of glucose on the brain.
Certain dietary patterns promote ketosis. For example, the Ketoflex 12/3 diet, a form of time-restrictive eating that limits the period during which a person eats to a 12-hour window at least three hours before bedtime, promotes the production of ketones. Watch this clip in which Dr. Dale Bredesen describes this novel dietary protocol and how it improves cognitive function.