Keto diet explained: A brief introduction to the Keto diet

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In practical terms, a ketogenic diet (“keto” for short) is an eating regimen that involves lots of fat, a moderate amount of protein, and a small amount of carbohydrates. A sustained diet of this kind will eventually bring your body into a state of “ketosis.”

In the most practical sense, the Keto diet, not unlike the Atkins diet and other types of diet/lifestyles in the category, preaches the consumption of high-quality fats in higher portions as compared to carbs. The idea is to bring your body (eventually) to a state of “ketosis.”

Which, in short, "is a metabolic state characterized by elevated levels of ketone bodies in the blood or urine. Physiologic ketosis is a normal response to low glucose availability, such as low-carbohydrate diets or fasting, that provides an additional energy source for the brain in the form of ketones."

Although the Keto diet or Keto lifestyle is nothing new, a recent emergence of younger folks looking to make better, healthier life choices has brought Keto and other types of diets back into everyday conversations.

As a result, we thought we would take a few minutes to answer some of the most basic Keto-related questions we hear all the time.

What Is the Keto Diet?

In practical terms, a ketogenic diet (“keto” for short) is an eating regimen that involves lots of fat, a moderate amount of protein, and a small amount of carbohydrates. A sustained diet of this kind will eventually bring your body into a state of “ketosis.”

Anyone who’s tried to lose weight or simply tried to eat better has faced frustration, mixed results, and borderline starvation. Keto embraces fat – big time! 75% of your diet is fat, yeah, FAT! Twenty percent is protein and only 5% of your diet is carbs. Wow, that sounds crazy (compared to the carb-riddled food pyramid). But, as you start to understand how your body processes calories, you’ll see that fat is where it’s at.

A keto diet is different for several reasons, but the main difference is that you won’t walk around feeling starved. Why? Fat is satiating! A keto diet isn’t about cutting calories (unless you want to for weight loss), it’s about the macros.

Fats – Ketone-Driven Metabolism, an Alternative Fuel Source

Consumption of dietary fat generates fatty acids that can immediately be used by most tissues for energy (the exception is the brain which can only use glucose or ketones for energy).

Excess dietary fats are stored as triglycerides (with unlimited storage potential). Under conditions of low carbohydrate intake (low blood glucose), triglycerides can be converted in the liver to ketone bodies.

Ketones are produced by the liver through beta-oxidation of fatty acids that can come from fats in our diet, as well as our own fat stores, and by a process referred to as hepatic ketogenesis.

The ketones referred to herein are actually biologically ketone bodies and include the molecules beta-hydroxybutyrate (BHB), acetoacetate (AcAc) and acetone (Ac).

What is Ketosis?

Ketosis is a normal physiological state that simply indicates that blood ketone levels are higher than normal. For example, under a typical American diet with high carbohydrate intake, blood ketone levels are usually at or below 0.5 mMol/L. Under these conditions, glucose provides the vast majority of fuel for the body.

During ketosis, however, ketones not only provide the majority of the body’s fuel, but may also offer numerous health benefits resulting from steady-state glucose and insulin levels, as well as increased satiety. During fasting or when consuming a high-fat, moderate protein, low-carbohydrate diet, the body generates ketones, derived from fat, for its energy source, leading to stabilization of blood glucose levels, and improved insulin sensitivity. The body is able to maintain normal blood glucose levels despite minimal to no carbohydrate consumption.

The liver uses gluconeogenesis to produce blood glucose from molecules that are not carbohydrates such as lactate, pyruvate, glycerol, and some amino acids. Essentially, the body does not need much dietary carbohydrate to obtain energy during a state of ketosis. Fats and ketones act as the body’s food/energy source in this state. During ketosis, once the body has utilized available dietary fats for energy, it will begin breaking down fat stores to achieve its energy requirements, triggering weight loss in the process.

Ketoacidosis is NOT Equivalent to Nutritional Ketosis

Diabetic ketoacidosis (DKA) is a dangerous medical condition observed primarily in type 1 diabetics and some type 2 diabetics. During DKA, ketone and (usually) glucose levels are extremely high, accompanied by a lack of insulin and low blood pH. During DKA, blood ketone levels (BHB: see methods of measuring ketones) can range from 3 to above 20 millimolar (mM) and blood pH decreases (< 7.3 and downwards to < 7.0). Blood glucose levels above 250-300 mg/dl or approximately 14 mM are also typically seen. In contrast, fasting ketosis can lead to levels of up to 8 mM ketones, < 100mg/dl glucose and have no significant impact on blood pH. Nutritional ketosis leads to ketones ranging from 0.5 to 3 mM, with mild fluctuations in blood glucose and no effects on blood pH.

Maintaining Ketosis

During ketosis, your body begins to break down your fat for energy rather than its normal source of fuel – carbohydrates. To maintain your maximal fat-burning state, you need to continue to maintain your state of ketosis. In order to do this, you need to ensure that you are tracking your protein intake, moderating your carbs to a minimum, and regularly testing your ketone levels to track your progress. You need to be diligent about tracking the macronutrients that you are consuming, otherwise you won’t be able to maintain your state of ketosis.

Methods of Measuring Ketones

Ketone levels can be measured with blood meters, breath testing, or urine strips. Note that the liver produces three main ketone bodies: beta-hydroxybutyrate (BHB), acetoacetate (AcAc) and acetone (Ac). Blood ketone meters measure BHB, the primary ketone body found in the blood.

Breath meters measure acetone, the ketone body produced by the breakdown of AcAc, and have been shown to correlate closely to BHB levels. Urine strips, on the other hand, measure acetoacetate , and are much less reliable for measuring ketosis, especially when the body becomes adapted to using ketones as the primary energy substrate (usually occurs after a few weeks of being in nutritional ketosis). Since the urine strips solely measure ketone excretion, the body excretes fewer ketones via urine once keto-adapted.

What Are Ketones

Ketones are viable sources of energy, and are produced by the liver during times of fasting, strenuous exercise, eating a low-carbohydrate/high-fat diet, and through ketone supplementation. A state of ketosis (becoming keto-adapted) is signaled by a rise in blood ketone levels.

During ketosis, ketones not only replace glucose as the primary energy source that the body uses, but ketones may actually be preferred over glucose by some of our most vital organs: the brain, the heart, and skeletal muscle.

Nutritional ketosis (natural physiological state when the liver is producing ketones due to a high-fat diet) offers a vast array of potential benefits for health and well-being, including weight loss, increased satiety, and optimized mental and physical performance.

There is also growing evidence that ketone supplementation and/or lowering dietary carbohydrate intake and switching to ketone metabolism through nutritional ketosis may protect the body from many common ailments.

How Do You Kick-Start Ketosis?

Know Your Macros: Macros are short for macronutrients, the nutrients that your body can use for energy. Macros consist of fats, carbohydrates, and proteins. Macronutrients make up the calories we consume – 1 gram of fat contains 9 calories, while protein and carbohydrates each contain 4 calories per gram.

In order to achieve nutritional ketosis through dieting, you must be within a specific macronutrient range. Even for a non-ketogenic, low-carbohydrate diet, having an idea of your macronutrient range is beneficial because excess protein can be converted to glucose.

Fortunately for many individuals, as the low-carbohydrate diet becomes more of a lifestyle, they’re able to rely less on strict macronutrient counting and can go more off intuition. In a standard ketogenic diet, the percentage of macronutrient distribution is 75% fat, 20% protein and only 5% carbohydrates.

Online calculators allow you to conveniently plug in variables like age, sex, height, and activity level to figure out how many daily calories you should consume. When starting a diet, calculating this number will involve some experimentation so expect to adjust as you go along. The important part will be understanding your macro ratios.

Count Carbs: counting carbohydrates is one of the most important steps when initially starting a ketogenic or low-carbohydrate diet. That’s because it’s deceptively easy to consume more carbohydrates than you might expect even while eating “healthy” foods. For instance, tropical fruits and juices are typically high in carbohydrates and, in many instances, these foods can exceed your daily carbohydrate intake when on a low-carbohydrate diet. In standard ketogenic diets, this number would equate to 20% of total calories from carbohydrates in a day. With other low-carbohydrate diets, while there isn’t a set number, 100 grams daily (or less) is generally considered to be “low-carb.”

Methods to Achieve Ketosis

Fasting Ketosis: Though difficult, fasting leads to ketosis. This is an evolutionary advantage considering the lack of a constant food supply prior to the agricultural revolution. As glycogen stores deplete, the body begins to break down fat stores to obtain energy. Short-term fasting (1-3 days) is an effective way to achieve ketosis. Medical supervision is recommended.

Dietary Restrictive Ketosis: Classic Ketogenic Diet: The most common, well-known method to achieve nutritional ketosis is via the ketogenic diet, in which the ratio of dietary fat to nonfat (carbohydrates and protein) is 3:1 – 4:1 (gram:gram). This concept has been tried in medical centers such as Johns Hopkins for over a century to treat drug-resistant epilepsy in children. The induction phase of the popular Atkins Diet also starts with a very high-fat ratio. Less restrictive ketogenic diets can have 3:1 or even 2:1 ratios, once the metabolic shift to ketosis is made. Typically, carbohydrate levels start at 10-15 grams per day, and then slowly go up over the course of several days to weeks to determine an individual’s carbohydrate tolerance. Some individuals (such as athletes) may be able to achieve nutritional ketosis while consuming up to 100 grams of carbohydrates per day, though many need to stay below 50 grams of carbohydrates to remain in ketosis. Liberal fat consumption typically provides enough energy.

Modified Atkins Diet: This diet is thought to be a more liberal version of the classic ketogenic diet, as it allows for more protein to be consumed. The ratio of fat to protein plus carbohydrates for this diet is 1:1 – 2:1.

Low Glycemic Index Diet: This diet may or may not induce ketosis, depending upon the blood glucose levels of the individual and the fat content of the diet. In this approach, carbohydrate-based foods (fruits, vegetables, grains) are selected based on their ability to raise blood glucose.

Protein and Ketosis: During nutritional ketosis, in addition to carbohydrate restriction and high fat intake, it is essential to moderate protein, as excess protein can be converted to glucose, and thus attenuate or prevent ketosis from occurring. Significant anecdotal evidence suggests that the consumption of too much protein on a low-carbohydrate diet can prevent or reverse ketosis. High quality saturated and monounsaturated fats are typically recommended while avoiding trans/hydrogenated fats.

Potential Side Effects

During ketosis, the kidneys excrete sodium and water more efficiently, leading to increased thirst and urination. Adequate hydration and electrolyte replacement are central to most ketogenic diets (particularly sodium, potassium, and magnesium). Without sufficient amounts of these vital nutrients, the “keto flu” is a very common side effect, and can be characterized by headaches, fainting, and fatigue, as the body switches from glucose to ketones as an energy source.

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