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The Ketogenic Diet: A Better Understanding

By this point, as is par the course with many diets, you have most likely heard plenty of ranting and raving over the ketogenic diet. Although this diet has historically been used to treat a variety of conditions, with the most notable being epilepsy, its popularity in recent years stems from the additional health benefits that people seem to experience on this diet. Before electing to follow a keto diet, however, you may want to know more. Why are carbohydrates so limited? What is ketosis and how is it maintained? What are some of the health benefits of this diet? Read on for a comprehensive breakdown of what the ketogenic diet entails and how to make it work for you.

Energy Production in the Body

There are three major nutrients, also called macronutrients, which provide energy for the human body. When these macronutrients are consumed, they are metabolized in the body and broken down into various building blocks for immediate (or later) use. The breakdown of these sugar, protein, and fat molecules also yields chemical energy that can be transformed into usable energy for cells. Generally, the energy from macronutrients is stored as adenosine triphosphate, or ATP. ATP is the primary molecule that the human body uses to provide cells with energy for our metabolism.

The most immediate source of fuel for the body is glucose but all three macronutrients can provide molecules for energy use. The ketogenic diet takes advantage of utilizing fatty acids, rather than glucose, for energy. When fatty acids enter the circulation, they can be integrated into cells and used to provide cellular energy. Depending on the state of the body, these fatty acids can also be metabolized into ketone bodies, which are another major source of fuel for tissues.

The Starve-Feed Cycle

When discussing nutrition, the human body cycles between two states in regards to metabolic changes – the starved state and the fed state, also called the starve-feed cycle. In the feed portion of the cycle, eating provides the body with fuel that can be used immediately or stored for later using during fasting. The starved portion simply refers to the fasting state that the body enters in-between feedings. Because body cells will die without adequate energy, the body must store fuel from eating and utilize it later for metabolic processes to continue.

As mentioned above, when we eat any of the macronutrients the body uses for fuel, they are digested and then released into the circulation to await their fate. When we consume carbohydrates, dietary glucose finds its way to the liver to be stored as glycogen, stored as fat in adipose tissue, or sent to the brain for use. When we consume protein, amino acids are sent into the blood to be used by cells for various roles, such as the disposal of ammonia via the urea cycle or the synthesis of important proteins. When we consume fat, triacylglycerols enter the lymphatic circulation and then the blood, where they are mostly broken down into fatty acids that can be stored in adipose cells.

Between meals, new fuel no longer enters the body and stored fuel must be used instead. As the body enters the early fasting state, the breakdown of glycogen and gathering of certain amino acids in the liver provides the cells with glucose to use for energy. Glycogen levels are greatly depleted in the liver after roughly 10-12 hours so at this point, the body must use alternate fuel sources when glucose cannot be easily synthesized for use.

Ketone Bodies as Fuel

When we eat carbohydrates, insulin levels spike in order to metabolize glucose and keep blood sugar levels steady. When we are in the fasting state and carbohydrate intake is low, less insulin is secreted by the pancreas. Lipolysis, the breakdown of adipose tissue to release fatty acids, is activated instead. The process of fatty acid conversion to ketone bodies occurs in the liver in multiple steps. First, fatty acids are activated to fatty acyl CoA outside of the mitochondrial membrane. Fatty acyl CoA is then transported into the mitochondria, where it is oxidized to acetyl CoA. This acetyl CoA can be converted into two primary ketone bodies: acetoacetic acid and β-Hydroxybutyric acid. When these ketone bodies leave the liver and enter other tissues, where they are converted back to acetyl CoA which can be used for energy.

⇒ A third ketone body, called acetone, is produced from acetoacetic acid. Acetone is only produced in small quantities and has a much lower concentration than the other two ketone bodies. Because it cannot be converted back to acetyl CoA for energy use in cells, it is not generally used for fuel and is instead excreted by the body.

Both acetoacetic acid and β-Hydroxybutyric acid are a huge source of fuel for the body when glucose is not available, such as during prolonged fasting or when there is a deficiency of insulin. Ketone bodies can be utilized by the heart, muscle, and brain. The use of ketone bodies over glucose can happen early on in the fasting state in almost all of the tissues mentioned except for the brain. The brain does not fully utilize ketone bodies initially, as fatty acids have a hard time crossing the blood-brain barrier. Instead, once the concentration of ketone bodies becomes high enough after 2-3 days of fasting, they can enter cross the barrier and begin to serve as fuel for the brain. Compared to other tissues, the brain does not exclusively use ketone bodies, so there is still a need for a small amount of glucose to feed the brain.

Metabolic Changes in Ketosis

The ketogenic diet takes advantage of this entire process by maintaining an incredibly low carbohydrate intake. After several days of this glucose “starvation” stage, the body compensates in various ways. By now, the concentration of ketone bodies is high enough for glucose synthesis in the liver to decrease. The amount of tissues utilizing glucose decreases and body tissues, including the brain, are now utilizing fatty acids and ketone bodies for energy. Glucose can now be synthesized by the kidney as well as the liver, as needed. The body no longer secretes as much insulin to meet blood sugar maintenance needs and instead secretes only small amounts. In addition, the amino acids needed for glucose synthesis during the fasting state decreases. Because of this, proteolysis (the breakdown of proteins) is restricted and the body utilizes less of the proteins found in enzymes and muscle tissue to create new amino acids.

This entire state of producing energy from the metabolism of fatty acids and ketones, often referred to simply as ketosis, can be maintained as long as carbohydrate intake is low – roughly 40g per carbohydrates per day or potentially much less, according to some sources. Although the initial thought might be to immediately cut the snack food and sugary drinks, it is important to remember that there are also healthy sources of carbohydrates, too. Healthy sources of carbohydrates include fruits, vegetables, whole grains, and legumes.

Following a Ketogenic Diet

The premise of the ketogenic diet is to maintain a state of ketosis through eating a diet low in carbohydrates, moderate in protein, and high in fat. When it comes to macronutrients, you will most commonly find this orientation: 5% carbohydrates, 25% protein, 70% fats. What does this macronutrient breakdown mean? It means that for all of the calories you consume throughout the day, 70% of them should be from fats, 25% of them should be from protein, and only 5% should come from net carbohydrates (total carbohydrates minus fiber).

⇒ You may be shocked to see such a high percentage of fat being recommended on this diet but you should know the truth about fats: not only are they absolutely necessary in a healthy diet, but a diet high in the right kind of fats can promote weight loss, reduce inflammation, and boast a plethora of additional benefits. Monounsaturated and polyunsaturated fats from a variety of food sources should be consumed often.

With so many common foods containing carbohydrates, it is important to educate yourself as to what can be eaten on a ketogenic diet. In general, this diet does not contain any grains or tubers. Most sugars, with the exception of certain sweeteners, are also off limits. Fruit is not consumed often, either. Instead, moderate amounts of meat and other protein sources, certain green vegetables and those vegetables grown above ground, and plenty of nuts, seeds, avocados, and healthy oils are the focal point. Essentially, it all boils down to eliminating food items that are high in net carbohydrates and instead building meals around fats and protein.

Maintaining a Ketogenic Diet

It is no surprise that the ketogenic can be an incredibly difficult diet to adjust to. The vast majority of people are used to consuming carbohydrates in some form, whether whole grain-packed meals, hearty vegetable and legume dishes, or fresh fruit snacks. This doesn’t include the large amount of people in modern society that also consume sugar snacks and drinks, baked goods, and other calorie-laden, carbohydrate-heavy meals. Cutting these types of foods down to the bare minimum is both a culture shock and a dietary choice that may be difficult to follow for the long-term. In fact, there is some claim that ketosis might even be a system shock, as well.

⇒ Undergoing the metabolic changes of ketosis can initiate a physical reaction with symptoms that feel akin to the flu – these symptoms are also known as the “keto flu”. They may include headache, nausea, fatigue, and GI disturbances, among other feelings of unwell. Although these symptoms are generally normal and not dangerous to a healthy body, a person should always consult with their physician before undergoing any drastic nutrition changes.

In addition, because ketosis does not occur unless carbohydrate intake is incredibly low (40g per day or possibly much less), falling out of this state can happen easily if even a small amount of extra carbohydrates are consumed. This leaves the body to begin the process of entering ketosis all over again – something that many find difficult to push through. Because the carbohydrate content of foods varies wildly, maintaining a state of ketosis can be a difficult task initially while adjusting to cutting back on the different food groups. All of the above issues can lead to difficulty with compliance, as is often found in overly-restrictive diets.

Still, there is often an accelerated weight loss that occurs in the first few weeks of ketosis due to an increased loss of body water. Because weight loss is generally a huge motivator in following any specific diet, initially at least, many people are able to push through the adjustment phase and learn how to follow the necessary restrictions.

Research Studies on Health Benefits

There have been a host of research studies performed utilizing the ketogenic diet for a variety of conditions, including epilepsy, weight loss, diabetes, and even athletic performance.

A review in the International Journal of Environmental Research and Public Health (2014) found that the weight loss from the ketogenic diet can potentially be caused by a multitude of reason. For one, eating higher amounts of protein can lead to greater satiation after meals, meaning that you can become full for less (in this case, calories). The state of ketosis can also have an effect on the hormones responsible for appetite, of which the actual ketone bodies may play a role. In addition, ketosis itself is a metabolic change that favors an increase in fat burning and a decrease in fat formation – this leads to an increase in what is known as metabolic efficiency, or how the body utilizes the energy from fat. Finally, because gluconeogenesis (the creation of glucose, as opposed to the intake of glucose) requires more energy and protein intake increases metabolic expenditure, the body’s metabolic cost is increased.

For those who are obese, the concern might be that an increase in fats may lead to greater health risks but in fact, quite the opposite is true. Studies have shown that carbohydrate reduction can lead to reduction in cholesterol and triglycerides and an increase in HDL levels, thus lowering CVD risk, among other things. The relationship between insulin response and health is an ever-evolving topic as well, but the nutrition community has been well aware of the health risks associated with increased insulin output and poor glycemic control for quite some time (see: type 2 diabetes). It would stand to reason that a diet low in carbohydrates that can improve insulin levels would most likely reap additional health benefits.

Ultimately, the research suggests that short-term ketogenic diets can have therapeutic effects for people with various health conditions, including weight loss, cardiovascular disease, type 2 diabetes, and epilepsy. It has also been studied for use with acne, PCOS, cancer, cognitive and neurological diseases, and other conditions – though much more research is needed to confirm the health benefits of a ketogenic diet for these conditions.


The internet is a truly amazing resource for anyone needing help with their diet. You can find research and explanations (like this article), tips and tricks, meal plans, and even communities for discussion and support – for literally any diet. If the ketogenic diet is something you are interested in trying out, feel free to check out some of the resources I’ve complied below.

  1. HealthlineThe Ketogenic Diet 101: A Detailed Beginner’s Guide
  2. Ruled.MeKetogenic Diet Food List: Everything You Need to Know
  3. BodyBuilding.comKetogenic Diet: Your Complete Meal Plan and Supplement Guide
  4. The Keto SummitFree Ketogenic Diet Meal Plan
  5. Diet Doctor –  14-day Keto Diet Plan
  6. Reddit/r/keto

Hopefully, these resources are a great starting place tow help you to determine if a truly low-carb diet is right for you and your body. And as always, be sure to pay your doctor or nutritionist a visit before undertaking any drastic lifestyle change!

Devlin TM. Textbook of Biochemistry with Clinical Correlations. 7th ed. Danvers, MA: John Wiley & Sons, Inc.; 2011.
Gropper S, Smith J, eds. Advanced Nutrition and Human Metabolism. 6th ed. Belmont, CA: Wadsworth Cengage Learning, 2013.
Lord RS, Bralley JA. Laboratory Evaluations for Integrative and Functional Medicine. 2nd ed. Duluth, GA: Genova Diagnostics; 2012.
Paoli A. Ketogenic Diet for Obesity: Friend or Foe? Int J Environ Res Public Health. 2014;11(2):2092-2107. doi: 10.3390/ijerph110202092. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3945587/.
Paoli A, Rubini A, Volek SJ, Grimaldi KA.  Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr. 2013;67(8):789-796. doi: 10.1038/ejcn.2013.116. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826507/.

Human Nutrition student working on her Master's, learning to love life through good food and good health.


  • ROJH

    Interesting read!! Everyone should take some time to read this one. It’s so important that we understand the truth about ketogenic diet. , I wanted to try keto diet, and I think you’ve cover everything I needed to know. I hope it works for me. I am can’t wait to get started with this new lifestyle. Thanks!

  • Santini

    Awesome article! This is absolutely worth reading. I’ve been wondering what really is keto diet and this article definitely gave me a better understanding about it. Thanks for sharing this information!

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