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Keto: A Diet for Your Body and Brain

Jonathan Vellinga, MD

While the holidays can be an amazing time of year, full of comfort and warmth, sometimes they can be overwhelming in terms of a healthy diet. Lots of baked goods, comfort foods, and snacks can leave even the most disciplined of us feeling as though we overindulged. It’s no wonder that one of the most popular New Year’s resolutions is to begin a new diet!

Keto Diet

A popular diet that is gaining more traction and adherents is the ketogenic (often shortened to just “keto”) diet. It is increasingly popular and has brought many people success in both feeling better and achieving their fitness and/or body weight goals. However, it may not be a good fit for others and can even be harmful to people with certain medical conditions.

What is a keto diet?

The keto diet is, at its most basic, a high-fat and low-carb diet that mimics starvation. While there are a few different types of ketogenic diets, the most popular version is 70% fat, 20% protein, and 10% carbs (1).

How does a diet high in fat mimic starvation?

The body generally relies on glycolysis to break down food for energy, which utilizes carbs. This is why most diets consist of 40-60% carbs - it’s easy energy, and the body is naturally in this state (1). However, when the body doesn’t get enough carbohydrates to fuel this process for an extended period of time, it switches its metabolic process to focus on breaking down fats to get energy. This process happens regularly during sleep or other extended periods of fasting. When the body is in this state consistently, the liver becomes more efficient at burning fat and thus supplying ketones (1). Ketones are one form of energy for your body and brain. This is part of the reason why many people also adopt intermittent fasting while on the keto diet. Intermittent fasting also helps the body become more efficient at producing ketones.

How can your brain switch the type of food it needs?

Well, the brain can’t make a direct 1:1 fat: glucose substitution. The brain does need glucose, but if all it has are ketones, the mitochondria of brain cells are able to break down fatty acids and derive glucose. Because this process is so regulated and more complex than glycolysis, fuel for the brain and body comes at a steadier rate, rather than an immediate spike (and subsequent crash) that can occur through the breakdown of carbs.

So, how does this affect your blood sugar?

Since the liver is able to produce ketones even while the body is fasting, and ketones are able to be broken down to produce glucose, blood glucose levels become more stable on the keto diet than on carb-heavy diets. These stabilized energy levels not only mean you more easily avoid post-lunch or sugar highs/crashes, but you actually can improve your brain health. Diets high in sugar result in fluctuating blood sugar levels, which reduce brain-derived neurotrophic factor (BDNF) levels, synaptic plasticity, and cognition- and mood-regulators in the brain (2). Synaptic plasticity, BDNF, and other regulators all contribute to a healthy brain that is able to function, learn, adapt, recall, emote, and build relationships. Fluctuating levels of blood glucose and hyperglycemia (chronically elevated blood sugar levels) can lead to the development of type 2 diabetes, which is a factor in developing Alzheimer’s and other brain diseases (3). (More information on the effects of blood sugar levels on brain health can be found in this article.)

Because diabetes is so often linked to excess weight as well as reduced brain health, it makes sense that studies are beginning to show that ketosis can help manage all three (4). Not only can keto help you lose weight (which itself can help manage diabetes), but some people who adopted a ketogenic diet used less medication to manage their diabetes even two years later (5).

So, limiting sugar - or eliminating it altogether - and maintaining healthy blood sugar levels can affect your health in a positive way. Beyond that, a keto diet paired with intermittent fasting can also create a neuroprotective reaction in your brain, helping fight harmful free radicals and neuronal cell death (also called excitotoxicity) (6). This neuroprotective reaction can help prevent and reduce symptoms of neurodegenerative disorders (6).

Other benefits of adopting a keto diet can include (1):

  • Weight loss

  • Lowered blood sugar

  • Improved insulin sensitivity

  • Reductions in diastolic blood pressure and triglyceride levels

  • Improved metabolic health

  • Decreased risk of heart disease

  • Slowed tumor growth

In addition to the above benefits, a healthy keto diet can improve (1, 2, 3, 7):

  • Symptoms and progression of brain diseases such as Alzheimer’s, Parkinson’s, etc.

  • Diabetes

  • Epilepsy

  • Polycystic Ovary Syndrome

  • Traumatic brain injuries

Is this diet too good to be true? What are some potential less-amazing side effects of keto?