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Ketosis: The Complete Guide

Published on: August 01, 2019

Ketosis: The Complete Guide

This is the first part of a series of guides that will deepen your knowledge of ketosis. We hope you’ll enjoy them! 

Did you know that when carbohydrates are no longer available in your body, it starts to burn its stored fat to produce an alternative fuel called ketones? This is what happens when you are in a starvation mode or follow a ketogenic diet.

People choose to go into ketosis because of its widely known benefits from weight loss to improved cardiovascular health.

However, ketosis has also gotten negative reactions from those who believe that carbohydrates are needed by your body to properly function. To shed light on this topic, this guide will show you everything you need to know.


What Is Ketosis?

Ketosis is a normal metabolic process where your body uses fat for energy instead of carbohydrates, which normally should be your body’s primary fuel source. In order to get energy, the fat in turn is broken down by the liver, producing ketone bodies through a process called ketogenesis. Ketones fuel your heart, brain, muscle tissue, and kidneys. As long as your body is deprived of carbohydrates, your body stays in a ketotic state [1].



Ketones: Types and Their Role in Human Metabolism

Ketones or “ketone bodies” are produced by your liver when there isn’t enough supply of glucose to turn into energy. There are three types of ketone bodies, namely:

Acetoacetate - Fatty acids are broken down by the liver, which then produces acetoacetate. That said, acetoacetate is the first ketone body created. It is then transported to your extrahepatic (meaning, “outside the liver”) tissues to provide energy.

Beta-hydroxybutyrate - Beta-hydroxybutyrate accounts for 78% of all ketones in the body. As the most abundant ketone, it is formed after acetoacetate is reduced [2]. Among the three ketone bodies, beta-hydroxybutyrate is the most interesting because it’s more energy-efficient than glucose.

Acetone - Acetone is the third ketone body, and also the least abundant [3]. It is formed spontaneously from acetoacetate and is excreted immediately through breathing. Testing for ketosis can be done by measuring breath acetone.



The Science Behind The Metabolic Process of Ketosis

Excess glucose from the food you eat is stored in the liver and muscles in the form of glycogen. Glycogen is the storage form of glucose that comprises of several connected glucose molecules.

There’s a limit to how much glycogen is stored in its original form. Excess glucose gets stored as fat with the help of insulin.

Whenever your body experiences a shortage of fuel in cases of food deprivation, it taps into your glycogen stores, through a process known as gluconeogenesis. As your glycogen stores run out, your body undergoes gluconeogenesis.

A further drop in the availability of glucose forces your body to undergo ketogenesis. At this point, ketone production by the liver becomes more active. Since insulin production is low at this point, fat storage is hindered.



What Are the Health and Medical Benefits of Ketosis?

Being in a state of nutritional ketosis, as a result of a well-formulated ketogenic diet, has many benefits [4]:

  • It decreases the risk of diabetes and improves diabetes management - Ketosis improves your insulin sensitivity due to a reduced intake of carbohydrates.
  • It decreases the risk of inflammation-associated diseases - Beta-hydroxybutyrate suppresses inflammatory pathways. Chronic inflammation is linked to heart disease, stroke, autoimmune disorders, and cancer [5, 6, 7].
  • Greater fat loss - Restricting carbohydrates in the diet boosts your sensitivity to leptin, your satiety hormone, that makes you feel full. As a result, your cravings reduce.
  • It protects the brain - Ketones provide an alternative fuel to the brain to maintain normal metabolism during metabolic stress [8].



Is Ketosis Safe? What Research Says

Most people benefit from being in nutritional ketosis as long as their diet is well-formulated [9].

People are often concerned about the impact of the ketogenic diet on heart health because of the widespread belief that eating high-fat foods increases plaque build up in the arteries. The opposite is actually true.

Evidence from human and animal studies show that the keto diet significantly reduces total cholesterol, increases HDL cholesterol levels, and decreases triglycerides and HDL cholesterol levels [10].

However, breastfeeding and pregnant women, and people with diabetes, kidney disease, pancreatic disease, muscular dystrophy, and eating disorders should seek medical supervision, prior to going on a ketogenic diet.



An In-Depth Look at The Ketosis Metabolism: What Happens Inside Your Body

Ketosis changes your metabolism. It trains your body to constantly run on a different energy source instead of carbohydrates. Your new fuel source are ketones, products of fat metabolism.

You can enjoy many metabolic advantages when you maintain ketosis. These benefits range from weight reduction to increased longevity.

Such metabolic effects result from decreased insulin and blood glucose. Ketone bodies, especially beta-hydroxybutyrate (BHB), lower inflammation. They also provide more energy than glucose.



Understanding the Long Term Effects of Ketosis and Keto Diet

While we know that following a keto diet over the short term comes with many benefits, much research studies are still needed to show its long-term effects. As with any lifestyle change, complying with the keto diet long-term can be an issue [1].

Many people can maintain ketosis for weeks to months, but many people also get in and out of ketosis from time to time.

For instance, a person can prefer more flexibility in his diet through carb cycling or will want to load up on carbs to boost athletic performance.



How Long Does It Take to Get into Ketosis

Achieving ketosis does not happen immediately. It can take anywhere from two days to one week depending on factors, including the person’s carbohydrate intake, his metabolic rate, exercise, and lifestyle.

For example, someone who normally eats a high-carbohydrate diet and lives a sedentary lifestyle before starting a keto diet, may take a week or longer to enter ketosis, unless he makes a drastic lifestyle change.



Do Low‑Carb Diets Lead to Ketosis?

Low-carb diets other than the ketogenic diet can achieve transient ketosis but not retain it over the long term since these diets are more lenient with their carb consumption. These low-carb diets include:

  • A typical low-carb diet
  • South Beach Diet
  • Atkins Diet

The keto diet is unique in that aside from limiting carbs, it requires you to get the majority of your calories from fat, while emphasizing quality fat sources.



The Science Behind How to Get into Ketosis

Here are a few things you can do to deplete your glycogen stores and increase your ketones:

Bring your carbohydrate intake down

Reducing your carbohydrates down to 20-50 grams per day is the most common approach. 20-50 grams of carbs is less than the amount in a medium plain bagel [11].

Eat more high-quality fats

It’s not just about eating more fats. Quality matters too.

Avoid artificial trans fats because they increase your LDL cholesterol (the bad cholesterol) and promote insulin resistance [12]. Trans fats are found in foods like fried potatoes, potato chips, cakes, and cookies [13].

Most of your dietary fats should come from monounsaturated fats. Sources include olives, avocados, and nuts. Polyunsaturated fatty acids contain omega-3 and omega-6 fatty acids. Good sources include fatty fish and nuts and seeds.

Practice intermittent fasting

Consuming little, or no calories or very few calories for an extended time period speeds up the breakdown of fats in your body and elevates circulating ketone levels. Additionally, glucose and insulin levels decrease [14].

Increase your physical activity

Your body experiences a depletion of glycogen supplies when we exercise. The intensity of your exercise influences how fast you enter ketosis. Considerable glycogen depletion happens during high-intensity activities [15].



What Are Optimal Ketosis and Ketone Levels?

When you follow a well-formulated keto diet, your blood ketone concentrations reaches 0.5 and 2 mmol/L. This can be seen as optimal levels for ketosis. Ketone concentrations can transientlyincrease to 3-5 mmol/L after exercise [16]. When ketone concentrations in your body get to 3 mmol/L, you experience maximum weight loss if weight loss is your goal.



Ketosis Side Effects: Most Common and How to Manage Them

Before you achieve the positive effects of a low-carb, high-fat diet, you’ll find yourself experiencing any of these unpleasant side effects:

  • Increased sugar cravings
  • Bad breath
  • Short term fatigue
  • Headache
  • Muscle cramps
  • Brain fog
  • Dizziness
  • Irritability
  • Digestive issues (diarrhea and constipation)
  • Flu-like symptoms
  • Insomnia
  • Frequent urination

These unpleasant symptoms happen as the body adapts to using fat as the main source of energy. They usually disappear within a few days to a month at most.

If you experience these side-effects, manage them by supplementing with electrolytes, drinking more water, maintaining good oral hygiene, getting adequate rest, and eating more healthy fats.



Ketosis Symptoms: Learn to Identify and Evaluate All Signals

Here are the common signs and symptoms to look out for that indicate that your diet is working:

  • Rapid weight loss - During the first few days of following a keto diet, you can lose a lot of weight. Since glycogen is bound to water, depleting your glycogen stores can make you lose water weight [17].
  • Increased ketone levels - Test your breath, blood, and urine for the presence of ketones. Blood ketone levels are the most reliable indicator.
  • Suppressed appetite - A loss of appetite means that your ketone levels have increased. A study showed that beta-hydroxybutyrate acts centrally in the brain to modulate appetite [18].
  • Improved focus and memory - A diet rich in healthy fats protects brain cells, resulting in decreased risk for brain deterioration. Omega-3 fats have anti-inflammatory and antioxidant effects on the brain [19].



Ketosis vs Ketoacidosis: Causes, Symptoms, and Takeaway

One might assume that nutritional ketosis and ketoacidosis are the same. No, they aren’t.

While nutritional ketosis is the normal and desirable metabolic state after following a low-carb and high-fat ketogenic diet, ketoacidosis is a life-threatening complication of Type 1 and Type 2 Diabetes Mellitus.

Take note that ketoacidosis is more common in Type 1 Diabetes. It is the result of non-compliance (non consistency) of diabetes treatment, illness, infections, and post-operative stress [20].

Diagnostic criteria and clinical signs and symptoms of ketoacidosis include the following [20, 21]:

  • Blood glucose reading above 250 mg/dl
  • Arterial pH below 7.3 (indicates increased acidity in the blood)
  • Nausea and vomiting
  • Dehydration
  • An altered state of consciousness
  • Kussmaul breathing (deep and labored breathing)
  • Fruity breath
  • Increased urination
  • Abdominal pain

People with diabetes who plan on starting a keto diet should first consult with a doctor or diabetes educator to get medical advice on avoiding triggers and following the diet properly.



Protein in the Keto Diet: How Much Is Too Much?

Protein intake on the ketogenic diet should be kept moderate. On a ketogenic diet, 30-35% of your daily calories come from protein [1].

Studies performed by Dr. Stephen Phinney and the Virta Team indicate that lean body mass and function are maintained on a keto diet with a protein intake of 1.5 and 1.75 grams per kilogram reference weight per day [22].

Eating more protein than what’s recommended on the keto diet can actually kick you out of ketosis. A high-protein diet increases the rate of gluconeogenesis, where the liver turns non-carbohydrate compounds (such as amino acids from proteins) into glucose [23].



Ketosis and Diabetes: What's Their Connection?

People with diabetes can benefit from the ketogenic diet. By reducing their dietary carbs, their blood glucose and insulin decrease to normal levels. In one study, patients with type 2 diabetes who followed a low-carb keto diet were able to reduce or discontinue their medications [24].

Ketones produced by the body in nutritional ketosis have the potential to lower inflammation, one of the underlying causes of diabetes [25]. Recent evidence suggests that the ketone body beta-hydroxybutyrate inhibits pathways involved in inflammation [26, 27].



Alcohol and Ketosis: What's Their Connection?

Some alcoholic beverages contain more sugar and carbs, which means that drinking them can put you off ketosis.

Alcoholic drinks that you should avoid include sweet wines, dessert wines, and dark beers. On the other hand, low-carbohydrate options include vodka, gin, whiskey, Pinot Noir, and Chardonnay.

Another way that alcohol (whether low-carb or not) throws you off the track is that it reduces your inhibitions and capacity for self-control by elevating norepinephrine in the brain [28].

That will explain why being under the influence of alcohol can make it easy for you to reach for that unhealthy high-carbohydrate food.



How Ketosis Affects Women

When it comes to females and ketosis, hormones are a hot topic.

Women often experience hormonal imbalances, and slight hormone alterations can impact their insulin sensitivity, mood, metabolism, energy levels, appearance, and reproductive health.

The keto diet fixes hormonal imbalances and improves a woman’s health in the following ways:

  • Polyunsaturated fatty acids (PUFA) reduces the risk of missed periods and irregular menstrual cycles [29].
  • Reducing carbs in your diet promotes insulin sensitivity which helps prevent diabetes and manage Polycystic Ovary Syndrome (PCOS) [30, 31].
  • By avoiding carbs and sugar, menopausal women can overcome weight gain that results from a decrease in estradiol [32]. The keto diet also reduces inflammation to reduce hot flashes.



Ketosis and Weight Loss: How Does This Process Work?

When you achieve ketosis, your body has depleted its glycogen stores and has become fat-adapted. Being fat-adapted means that your body now derives its energy needs on its fat stores rather than on dietary carb sources for energy.

Ketones produced as a result of fat breakdown, such as beta-hydroxybutyrate and acetoacetate, produce a satiating effect [18].

People who maintain a low-carb, high-fat diet lose more fat as the diet keeps their insulin low. High-carb foods lead to higher insulin levels, and insulin promotes fat storage and increases hunger [33, 34].



Ketosis and Bodybuilding: Can You Build Muscles on Keto?

When it comes to fitness, people are wondering whether they can lose fat and also build muscles. It is possible to add muscle mass on keto, but it’s not as simple as reducing carbs and eating more fat.

There are various factors that impact your muscle gain on keto:

  • Protein consumption - It’s no secret that amino acids stimulate protein synthesis in muscles [35]. When going on keto, athletes and bodybuilders should make sure that they consume enough protein to increase muscle mass without stimulating gluconeogenesis.
  • Keto diet variation - People who engage in high-intensity training benefit from consuming carbs strategically to get an energy boost. Consider the targeted ketogenic diet (TKD).
  • Electrolytes - Being in ketosis depletes electrolytes which will result in muscle cramps. Supplementing with electrolytes such as sodium, potassium, magnesium, chloride, and chloride support muscle function [36].



Ketosis and Exercise: How Can Exercise Boost Ketosis?

Recall that glycogen acts as a storage form for glucose mainly in the muscles and liver. Exercising is an effective strategy for quickly using up your glycogen stores. The greater the exercise intensity, the greater the depletion. To replenish your glycogen stores, you need to eat carbohydrates [15].

Depriving yourself of carbs keeps those glycogen stores from filling up after exercise, and so your body starts to convert its stored fat into ketone bodies for fuel. One study showed that exercising before meals elicited post exercise ketosis [37].


Therapeutic Ketosis Applications: Science-Based Facts

Diet-induced ketosis has been used over the years as a therapy for various conditions.

Since the 1920s, physicians introduced very low carb ketogenic diets to mimic the metabolism of fasting and treat epilepsy. Now, they’re being used to minimize the risk of or manage diseases such as diabetes, obesity, polycystic ovary syndrome, acne, neurological diseases, cancer and respiratory and cardiovascular disease [38].


  1. Masood W, Uppaluri KR. Ketogenic Diet. Last update: 2019 March 21 -
  2. Qiao Y et al. Breath Ketone Testing: A New Biomarker for Diagnosis and Therapeutic Monitoring of Diabetic Ketosis. 2014 May -
  3. Laffel L. Ketone bodies:... View all references

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