Facts & Fallacies on the Ketogenic Diet, Part 3

With the growth in popularity of the ketogenic diet, we wanted to get the facts on how it works, who the ideal candidate is, and what the misconceptions are. We talked to three experts on the topic; our third interview was with Jeff Volek, PhD, RD.

What sparked your interest in the ketogenic diet?

My interest really goes back to a time in the early ’90s when I personally switched to a ketogenic diet and had a very positive experience.

This happened while I was completing my dietetic training and transitioning into a graduate program where I was part of a very dynamic lab studying a variety of diet and exercise interventions. I started performing experiments on ketogenic diets in humans in the mid-1990s. The results were positive and led to many other follow-on studies over the last 20 years that have been published in probably 40 or 50 scientific papers. It’s really an exciting area of research that will continue to be studied by a wide variety of scientists in different disciplines in an attempt to more fully understand the clinical and performance applications of keto-adaptation.

What role do ketone bodies play in the ketogenic state?

This really goes back to the beginning of humans on this planet, when we did not have a continuous supply of food like we do today. We needed to have a way to produce alternative fuel when we didn’t have glucose available because the brain primarily relies on glucose as a fuel. So we developed this process of ketosis, which are products of fat metabolism. Approximately two-thirds of the energy demands of the brain can be met by ketones, so we can dramatically reduce our requirement for glucose if we are in a state of nutritional ketosis.

We’re also discovering a whole range of other potential roles and functions of ketones as signaling molecules, so they’re acting more like hormones and affecting gene expression. This is really exciting because it opens up a whole new perspective on the potential health benefits and even performance benefits of ketosis.

Why do athletes use the ketogenic diet?

For decades, we've been promoting high-carbohydrate diets to athletes and telling them they need to carbo-load in order to perform optimally, yet when you're keto-adapted, you essentially double your rate of fat burning. And being able to tap into that fuel source more efficiently and oxidize fat more efficiently is a huge advantage, especially for ultraendurance athletes who may be running or cycling for many hours. Eventually you run out of glucose.

Another common response to a ketogenic diet is, people lose weight. If they lose body fat and still retain their muscle, they improve their power-to-weight ratios. They're more efficient. They're also just healthier. The other really common claim we hear from athletes is that they recover faster. I think this is likely due to the fact that ketogenic diets decrease oxidative stress. We have a lot of clinical observations supporting that. Exercise is an inflammatory stress, and it increases oxidative stress. If you minimize that or mitigate it to some extent by being keto-adapted, then that logically translates into a faster recovery.

What is the recommended timeframe to adhere to the diet?

There is a certain time period required to fully adapt to the ketones that are produced and to make the physiologic changes that occur when a person is keto-adapted. Within a couple of days, ketone production increases, and ketone levels in the blood are elevated in most people, but it takes several weeks for the cells to restructure themselves and change the metabolic machinery in a way that allows them to fully oxidize ketones and fatty acids.

We know there's a 3-4 week period that is required to fully adapt. But it may take even longer for some of the more subtle adaptations to occur in mitochondria and so forth. We often hear from athletes after six months or even a year that they continue to adapt and experience additional benefits.

Are there any symptoms that would be a cause for concern?

There will be some people who experience a rather large increase in their cholesterol levels. We don’t think this is associated with an increase with atherosclerosis because at the same time, HDL cholesterols improve, triglycerides go down, the quality of the LDL particles improve, meaning the small LDL particles decrease, and those are the more atherogenic particles.

What’s the best way to measure a successful keto-adaptation process? What levels should be achieved?

Probably the most important marker to look at would be ketones in the blood. A general threshold that we use to say that someone is in nutritional ketosis is 0.5 millimolar (mM) beta-hydroxybutyrate levels in the blood.

To put that in perspective, someone who’s eating more than 100 grams of carbohydrate rarely sees their ketones go above 0.2 mm; they’re often under 0.1 mm. Most people will find themselves between 0.5 mM and maybe 1.5 or 2 mM when they’re consuming 40 grams of carbohydrate and consuming moderate protein.

Having a measure of glucose can be helpful. If you have access to an insulin value, that may also be informative. If you have access to measuring fat oxidation rates using indirect calorimetry, that would be a good indication a person is on the path to being keto-adapted. If they have a low respiratory exchange ratio that tells you they’re burning primarily fat for fuel, and that correlates highly with ketosis.

What role do MCT oils play in the support of a ketogenic program?

Medium-chain fatty acids are specific types of fatty acids that contain 6, 8, 10 carbons, and some consider the C12 a medium-chain fatty acid as well in contrast to the much more common dietary fatty acids that are 14, 16, and 18 carbons.

Metabolically, the medium-chain fatty acids are metabolized very differently. They’re not stored in membranes in appreciable amounts, so as a result, the medium-chain fatty acids get converted to ketones at a higher rate than long-chain fatty acids. One might wonder if including a lot of medium-chain fatty acids would enhance the effects of a ketogenic diet.

Keep in mind, the ketones produced from them would not be coming from adipose tissue. This would be ketones produced from the ingestion of these medium-chain fatty acids. They can be used in small amounts. At higher doses, they can have some undesirable GI effects, but they can be a part of a well-formulated ketogenic diet.

For more keto Q&A, read part 1 and part 2 of this series.

About Jeff Volek, PhD, RD:
Jeff Volek, PhD, RD is a registered dietitian and professor in the Department of Human Sciences at the Ohio State University. For the last two decades, he has performed cutting-edge research elucidating on how humans adapt to diets restricted in carbohydrate with a dual focus on clinical and performance applications. His work has contributed to the existing robust science of ketones and ketogenic diets, their use as a therapeutic tool to manage insulin resistance, plus their emerging potential to augment human performance and resiliency. Dr. Volek has secured research funds from federal sources, industry, and foundations. He has been invited to lecture on his research over 200 times at scientific and industry conferences in a dozen countries. His scholarly work includes 300+ peer-reviewed scientific manuscripts and five books, including a New York Times Best Seller.


This content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Individuals should always consult with their healthcare professional for advice on medical issues.

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