Rules on what to eat can be confusing for many as there are many dietary approaches that are touted to be beneficial to your health and your waistlines yet often conflict with one another with regards to what one should eat. I am often asked for nutritional guidance in my clinic and the most recent trend for thought is the ketogenic diet.

The ketogenic diet has been around a long time. It is commonly used for refractory seizure disorders (epilepsy) and evidence of its efficacy for epilepsy dates back as far as at least 1921. There are many different types of the ketogenic diet including the classic ketogenic diet, the medium-chain triglyceride (MCT) diet, the modified Atkins diet, and the low glycemic diet. Because fasting is a rapid method of achieving “ketosis,” intermittent fasting diets can also be ketogenic depending upon how it is accomplished.

But what is ketosis? Here are simple scientific facts I explain to my patients:

  1. In ketosis, human metabolism switches its main energy source from carbohydrates to fatty acids and ketones once the storage form of glucose – glycogen – is used up.
  2. The fat cells break down triglycerides into fatty acids (of different chain size) and those fatty acids are used as the energy source by the liver and muscles.
  3. The liver cells take the fatty acids and oxidize them into ketones which are used as the energy source by the brain, muscles, and other tissues.
  4. Ketones are in the form of acetoacetate, acetone, and beta-hydroxybutyrate. Beta-hydroxybutyrate serum levels are a reliable measurement of ketosis.
  5. Physiologically, it does make a difference how one achieves ketosis whether it is via high fat intake, fasting, or reduction of carbohydrates. For example, if one remains on a high fat diet for a long period of time and decides to fast a day, ketone concentrations will drop because their body is dependent on the high fat intake.

Ketosis can be neuroprotective in the short term by improving mitochondrial function but has not shown to have beneficial long term effects and not considered a healthy approach to weight loss. In fact, epilepsy patients on the ketogenic diet for seizure control are medically monitored. Side effects can include nausea, vomiting, constipation, fatigue, acid reflux, kidney stones, elevated cholesterol and triglycerides, vitamin deficiencies such as calcium and other water-soluble vitamins, and atherosclerosis.

It is also not known if the consumption of ketones from foods packaged with ketones, such as acetoacetate, have similar physiologic effects. Ketones are not found in food sources. The complex metabolic reactions that take place within the body to produce and utilize these ketones cannot be undervalued. Ketosis can only be achieved by feeding the body the necessary substrates while avoiding the foods, such as carbohydrates, that counteract the body’s attempts to find and make alternative energy sources.


Respecting our natural physiology is important. Intermittent ketosis is likely safe and neuroprotective in healthy individuals but long term ketosis can cause adverse effects and poor health. Speak with your physician when considering any significant change in dietary patterns.


The most important thing we can do is listen to our bodies. If we listen closely enough, we will know what it needs to achieve our own personal optimal health.

You may also like