At its simplest, a ketogenic diet is a very low carbohydrate, high fat, moderate protein diet. The purpose of following a ketogenic diet is to put the body into a state of ketosis where the body relies on burning fat for fuel instead of sugar.
See, the body has two major fuels – sugar or fat.
Today, most people exist primarily in the sugar-burning state due to constant access to food and high carbohydrate diets.
Carbohydrates are broken down in the body to glucose, and it is this glucose that is used by our cells as fuel. Turns out that although glucose is essential to survival, carbohydrates are not since we the body is designed to generate all the glucose it needs, even in a fasted state.
The ketogenic diet dramatically reduces the amount of carbohydrates in the diet, shifting to fat as an alternative fuel. Ketones are a by-product of accelerated fat burning, but we only produce them carbohydrate restriction, or fasting for extended periods of time. This is because the brain demands a constant supply of energy, and in a carbohydrate-fed state, the brain relies exclusively on glucose for fuel. So, when glucose and glycogen levels fall, the brain needs an alternative fuel. However, because the brain can’t directly use fat for energy (except for MCTs), the liver converts fat to ketone bodies to sustain brain energy metabolism. Ketones also serve an anti-catabolic function as a survival mechanism to spare our skeletal (and cardiac) muscle tissue from being broken down for glucose, so in this way the ketogenic diet is also muscle-sparing.
The ketogenic diet is unique from any other diet in that it is the only diet defined by the presence of an elevated biomarker, defined as hyperketonemia (elevated beta-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone). When we are in a state of ketosis, ketones can be found in our blood, urine, and breath, and measuring their presence is used to determine if your diet is ketogenic, since an elevation of blood ketones defines ketosis, and achieving ketosis defines a ketogenic diet.
The origin of the ketogenic diet dates back to the early 1900s and was designed to mimic the metabolic state of fasting. At the time, fasting was being used to control seizures in epileptic patients, but as soon as these patients resumed their normal diet, their seizures would return. Scientists figured out that replacing carbohydrates in the diet with fat tricked the body into behaving as it would in the fasted state – triggering the body to make ketones – and thus the diet was coined the ketogenic diet. Over the past century, the diet has evolved and its applications have expanded tremendously. Many people turn to the ketogenic diet for weight loss, but if you browse the articles on our blog you will see that the benefits of ketosis extend far beyond weight loss, although if that is your goal then it can work pretty well for that, too!
So, what do you eat on a ketogenic diet?
When following a well-formulated ketogenic diet, your nutrition will be coming from quality foods like avocado, eggs, meats, fish, grass-fed butter, nuts and seeds, extra-virgin olive oil, leafy greens, and fibrous/non-starchy vegetables. Carbohydrates on a ketogenic diet are typically capped at a total of 50g, and protein can range from 1-1.8 g/kg of goal body weight. The remaining calories will come from fat, and it’s recommended that fat is eaten to the point that you are satisfied or to your personal caloric needs.
The general macronutrient breakdown ranges from:
· 65-85% fat
· 15-35% protein
· 0-10% carbohydrates
Everyone’s ketogenic diet will look a little different because we all have different bodies and lifestyles that influence our ability to achieve ketosis, and that’s why these ranges seem quite broad. The more you experiment with a ketogenic diet, the more you will learn how to modify your intake of each macronutrient to best suit your body and your goals.
Limiting carbohydrates is the most essential component of following a ketogenic diet because it is the low levels of glucose that initiates the cascade of reactions that eventually result in ketosis, and overeating carbohydrates just a little bit can be enough to shut down ketogenesis (the production of ketones).
General Keto Food List
– Fatty cuts of meat
– Poultry with skin
– Fatty fish
– High quality oils (e.g., coconut oil, extra-virgin olive oil, avocado oil, MCT oil)
– Low-sugar berries (e.g., wild blueberries)
– Nuts & seeds
– All leafy greens and lettuces
– Cruciferous vegetables (e.g., broccoli, cauliflower, Brussel sprouts, cabbage)
– Other produce: celery, cucumber, mushrooms, zucchini, onions, garlic, etc.
How do you know if you’re in ketosis?
There are three primary ways to measure ketones. Generally, ketosis is defined by a blood level of BHB at or above 0.5 mmol/L.
1. Blood ketones
The most accurate way to measure ketosis is to measure blood ketones, which tests for BHB. This requires a blood ketone meter and ketone strips.
2. Urine ketones
Urine ketone strips test for the ketone, AcAc, but the accuracy of this method varies on how long you have been following a ketogenic diet and hydration status. Ketones can end up as “waste” in the urine after being filtered through the kidneys, depending on the body’s energy needs. In the beginning stages of a ketogenic diet, testing urine ketones can be quite accurate, but as you become more keto-adapted, and therefore better at using ketones as fuel, you excrete less in the urine. Thus, testing urine ketones at this stage isn’t representative of your level of ketosis.
3. Breath ketones
Technological advancements have brought to the market a number of breath ketone meters that represent an easy and accurate way to test for ketosis. These meters test for the ketone acetone excreted on our breath, which may also make your breath smell “fruity.”
Besides objective measures to test for ketosis, increased and sustained energy levels, reduced appetite, mental clarity, and “fruity breath” may be indicators that you are in ketosis.
Check out our other blog articles to learn more about the applications of nutritional ketosis!