Why does the Alzheimer's brain lose the ability to use glucose — and how does a ketogenic diet help manage the disease?
In Alzheimer's disease, the brain undergoes a profound metabolic crisis: it progressively loses the ability to use glucose as its primary fuel source. In response, astrocytes begin breaking down the myelin sheath to produce ketone bodies as an alternative energy source for brain cells. A ketone-rich diet or exogenous ketones, combined with aggressive exercise and high omega-3 fatty acid intake, are recommended to support the brain through this crisis.
Key concept from the episode
Astrocytes & the myelin sheath
Astrocytes are support cells in the brain that, under metabolic stress, can break down the myelin sheath — the fatty protective layer surrounding neurons — to produce ketone bodies. These ketones then serve as a backup fuel source when glucose metabolism fails, as occurs in Alzheimer's disease. The white matter of the brain, where myelinated neurons live, is particularly vulnerable to this process, and white matter lesions are a recognised marker of neurological decline.
The metabolic failure in Alzheimer's is not simply a side effect — it is a central feature of the disease. Because the brain can no longer efficiently extract energy from glucose, providing an alternative fuel becomes a genuine therapeutic strategy rather than a lifestyle preference. A ketogenic diet, by shifting the body's primary energy substrate toward ketones, directly addresses this energy gap. Exogenous ketone supplements can also be used to achieve the same effect without a full dietary overhaul.
Exercise is the third pillar alongside ketones and omega-3s. The SMART trial demonstrated that resistance training two to three times per week in people with mild cognitive impairment not only preserved cognitive function but enhanced processing speed and fluid intelligence — and measurably slowed grey matter loss. The genetic risk factor ApoE4 raises the stakes considerably: one copy increases Alzheimer's risk two to three times for males and sixfold for females; two copies push that risk to ten times for males and fifteen times for females. Yet even carriers can meaningfully reduce their risk through metabolic and lifestyle interventions. You can explore the full episode and related discussions on Listenly's Diary Of A CEO page.
"Having strong legs is by far the most important tool in your toolbox for the prevention of Alzheimer's disease."
— Steven Bartlett, The Diary Of A CEO with Steven BartlettSee also
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