A ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that forces the body to burn fats rather than carbohydrates, for energy requirements. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body as energy. However, if there is very little carbohydrate in a diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies replace glucose as an energy source. An elevated level of ketone bodies in the blood, a state known as ketosis. (1)

In Keto Clarity, the authors define Ketosis as “a metabolic state that happens when you consume a very low-carb, moderate-protein, high-fat diet that causes your body to switch from using glucose as its primary source of fuel to running on ketones. Ketones themselves are produced when the body burns fat, and they’re primarily used as an alternative fuel source when glucose isn’t available. In other words, your body changes from a sugar-burner to a fat-burner. Depending on your current diet and lifestyle choices, becoming keto-adapted can take as little as a few days and or as much as several weeks or even months. So “being in ketosis” just means that you are burning fat.” (2)

(1) Ketogenic diet, from Wikipedia.

(2)  Moore, J., Westman, E. MD (2014). Keto Clarity: Your Definitive Guide to the Benefits of a Low-Carb, High-Fat Diet. Victory Belt Publishing at page 32.

The authors of Keto Clarity quote Dr. William Wilson, a family practitioner and expert on nutrition and brain function, who explained that “throughout most of our evolutionary history, humans used both glucose and ketone bodies for energy production.” He said that our Paleolithic ancestors used glucose as their body’s preferred fuel when non-animal food was available, but during periods of food shortage or when animal-based foods were their primary source of calories, want to take a wild guess at what was sustaining them? You guessed it—ketones! “Thus, our ancestors spent most of their time in a state of ketosis,” Dr. Wilson concluded. He added, “If our early ancestors hadn’t developed a way to use ketones for energy, our species would have ended up on Darwin’s short list eons ago!” (1)

In the leading book in this area,The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-Saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable (2) the following passage is reassuring to those considering the safety of a Ketogenic Diet. Some confuse nutritional ketosis with the medical condition known as “keotacidosis” that diabetics may experience:

“Nutritional ketosis is by definition a benign metabolic state that gives human metabolism the flexibility to deal with famine or major shifts in available dietary fuels. By contrast, ‘diabetic ketoacidosis’ is an unstable and dangerous condition that occurs when there is inadequate pancreatic insulin response to regulate serum B-OHB. This occurs only in type-1 diabetics or in late stage type-2 diabetes with advanced pancreatic burnout. In this setting of deficient insulin, when exogenous insulin is withheld, serum B-OHB levels reach the 15-25 mM range –5-to-10-fold higher than the levels characteristic of nutritional ketosis. Unfortunately, among the general public and even many health care professionals as well, these two distinct metabolic states tend to be confused one for another. Understanding how different they are is key to being able to capture the many benefits of nutritional ketosis while avoiding the risks in that very small minority of the population subject to developing diabetic ketoacidosis.”

(1)  Moore, J., Westman, E. MD (2014). Keto Clarity: Your Definitive Guide to the Benefits of a Low-Carb, High-Fat Diet. Victory Belt Publishing at page 33.

(2) Volek, J., Phinney S., (2011). The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-Saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable, Beyond Obesity LLC

When a person’s metabolism burns sugar for fuel, it can’t easily access stored fat for energy and that means that your muscles cannot oxidize fat. For example, long distance runners will carb load and will use up their glycogen stores during training or a race. Further, the liver can only store about 50–90 grams of glucose for energy conversion. This means that recharging glycogen stores is necessary when you burn sugar, whether you are running a marathon or reaching 5 pm at the end of your work day. The downside of being a sugar burner is that you constantly need and crave carbs, and for many people, especially those who are not marathoners, more fat is stored on the body than burned, especially when insulin levels are high in reaction to carbs and sugar intake that exceeds demand.

However, if you adapt your body to run on “ketone bodies”, produced by the liver from fatty acids when following a Ketogenic Diet, your fat tissue will release fatty acids 4 to 6 hours after eating and during fasting and you can also effectively oxidize both stored fat and dietary fat for energy. The body becomes adapted to use fat, and not glucose, for fuel.

Author Maria Emmerich states in Keto-Adapted, “Keto-adapted (or fat-adapted) means you can rely more on fat for energy during exercise, which means sparing glycogen for when you really need it. Being able to mobilize and oxidize stored fat during exercise reduces an athlete’s reliance on glycogen. This helps athletes save the glycogen (which your body can make from protein, too) for the truly intense segments of a session, and burn more body fat.” (1)  This applies equally to the energy required to run your body around the clock, whether you are at work or the gym.

(1) Emmerich, M., ( 2013) Keto-Adapted at location 287.

An excellent resource is Ketogenic Diet: Ketogenic Diet Mistakes you need to Know (1).  Some common mistakes made when starting a Ketogenic Diet include:

  1. Ignoring or consuming unlimited calories, especially if trying to lose weight;
  2. Being too pre-occupied with your scale weight, as opposed to looking at body fat or muscle composition;
  3. Using urine testing vs. the more reliable blood testing to measure Ketones levels to know if you are in a state of Ketosis;
  4. Over-consuming carbohydrates, especially in the Ketosis start-up phase;
  5. Consuming too much protein to start or maintain Ketosis due to causing gluconeogenesis (where the liver converts protein to glucose);
  6. Being fearful of consuming too much fat (including healthy fats, like those found in avocados, olive oil, coconut oil, fatty fish);
  7. Not protecting your electrolyte balance by maintaining adequate sodium, potassium and magnesium levels;
  8. Not giving your body sufficient time to convert from being a sugar burner to a fat burner (from a few days to 3-4 weeks is normal);
  9. The need to reduce stress levels and maintain healthy sleep patterns;
  10. Not incorporating a healthy exercise regime, without overtraining or pushing your body before it is ready.

(1) Givens, S. (2015).  Ketogenic Diet: Ketogenic Diet Mistakes you need to Know. Amazon Digital Services, Inc.