What is Ketosis?

Written by Kate Harrison

Fact Checked by: Roger Thomas

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Ketosis is a normal bodily process. When your body doesn’t have enough glycogen to burn as energy (taken from dietary carbohydrates), it switches over to burning up fat for fuel. It does this by converting fat into ketones.

Ketosis is elicited through a ketogenic diet. It’s common for those suffering from certain medical conditions to be prescribed it. It’s also a very good weight loss and weight management tool by which many people swear.

The Ketogenic Diet

keto foods in a pan

A ketogenic diet is structured entirely to elicit ketosis. Ketosis relies on you severely restricting your dietary carbohydrate intake. This means that a ketogenic diet plan will include very few carbs (generally 50g or below per day, which is the equivalent of a couple of bananas). You’ll also eat moderate amounts of protein, whilst taking the majority of your calories from healthy fats.

Common foods eaten on a ketogenic diet include meat, fish, butter, eggs, cheese, cream, oils (olive, sunflower, coconut, rapeseed, and so on), fatty greens like avocados, low carb vegetables like spinach, seeds, and nuts.

You’ll be leaving out heavy carbohydrate sources like grains, rice, sugar, beans, potatoes, milk, fruit, breakfast cereals, and most high-carb vegetables.

With this in place, your body will quickly use up your glycogen reserves, before entering the metabolic state of ketosis. At this point, your body will begin to turn fat into ketones, which will act as your main energy source.

Your body will become very efficient at creating and using ketones within a few days or weeks of entering ketosis. This will represent a great way of losing body fat. It also helps to lower insulin levels, which can improve insulin sensitivity and blood sugar balance.

The Science Behind Ketosis

Our bodies typically rely on glucose for fuel when we follow high-carb diets. Glucose comes from carbohydrates, including common sugars and starchy foods like bread and certain vegetables.

In restricting these food sources, you restrict your body’s glucose supply. This forces it to seek out alternative energy sources. It turns to fat, which can be broken down into ketones. When your body is using ketones rather than glucose for energy, it is in a state of ketosis.

We often experience ketosis outside of ketogenic diets. Periods of fasting or hunger, or bouts of strenuous physical effort, will often trigger it as our glucose supplies run out. However, a ketogenic diet will force your body to use ketones as the dominant energy supply.

Your body will produce two main ketone bodies during ketosis. These are acetoacetate and beta-hydroxybutyrate, though it will also produce smaller amounts of acetone. These provide the brain, heart, and muscles with energy in the absence of glucose.

Ketosis vs. Ketoacidosis

Ketosis can be dangerous in certain situations. Ketones can build up, lead to dehydration, and can change your blood’s chemical balance; it can become acidic, which can in turn cause coma or death. This is ketoacidosis.

Those suffering with diabetes can experience ketoacidosis (called diabetic ketoacidosis, or DKA) when they don’t take appropriate insulin doses, when they are sick or injured, or when they are dehydrated.

Ketoacidosis can happen to those without diabetes, too. It can occur because of alcoholism, starvation, or overactive thyroid function.

It generally won’t occur on a healthy low-carb diet where there are no additional health concerns.

This being said, there are some ketoacidosis symptoms to watch out for. These include dry mouth or excessive thirst, excessive urination, fatigue and lethargy, dry or flushed skin, stomach concerns, including vomiting and belly pains, breathing difficulties, bad breath, and confusion.

If you experience any of these symptoms when following a ketogenic diet, you should consult your medical provider immediately.

Ketosis For Weight Loss

A ketogenic diet can be perfect for losing weight or maintaining bodyfat levels. It can help you to burn through your body fat reserves, preserve lean muscle mass, whilst decreasing your chances of suffering from many diseases.

Studies have suggested that ketosis may be more effective for weight loss than low fat diets, though calorie intake will generally need to be restricted. They may also be good for reducing your appetite. In leveling out your blood sugar levels, it will stop energy crashes and hunger pangs, making it easier to maintain a calorie deficit.

It’s easier to naturally maintain a calorie deficit through ketosis, too, meaning that you won’t have to track calories to ensure that you are eating for weight loss (though, of course, you will have to track macronutrients, particularly carbohydrates, to ensure ongoing ketosis).

How Does Ketosis Work For Weight Loss?

There are a few mechanisms by which ketosis can help with weight loss.

Firstly, they inspire you to take in a lot of protein. Though fat will be your dominant macronutrient, you will still be eating far more protein than a standard Western diet will promote. High protein intake alone has been shown to aid in weight loss – it is a slow burning form of energy, diminishes hunger pangs, increases satiation, and promotes lean muscle mass growth.

Fat is also a slow burning energy source, further aiding satiation. Ketogenic diets also elicit positive changes in the hormones that regulate our appetites, including leptin and ghrelin, further suppressing hunger.

As we have seen, ketogenic diets can improve insulin sensitivity. They can do so to such an extent that they are often recommended for those suffering with diabetes as a way in which to manage their symptoms. This improved sensitivity can also improve energy utilization and boost your metabolism.

steak and vegetables for keto

Some research suggests that a ketogenic diet may even decrease your ability to store fat. It may reduce lipogenesis, the process by which sugar is converted into fat. Without excess carbs, however, this can’t be done, and fat is then used as energy.

This leads us into increased fat burning potential. Ketogenic diets may slightly increase the amount of fat you burn, though the data is tentative here.

Finally, ketosis causes gluconeogenesis – it converts fat and protein into usable carbs for energy. This is a calorically intense process, which may mean that more calories are burned daily.

All of these combine to make a ketogenic diet potentially very effective for maintaining healthy body composition.

Health Benefits of Ketosis

Weight loss and management are far from the only uses of a ketogenic diet. There are plenty of health benefits to be gained from spending the majority of your time in a state of ketosis.

One of its main medical uses is in the prevention of seizures, which it has been proven to do ably. For this reason, doctors may prescribe a ketogenic diet for epileptic children. Epileptic adults may often also benefit from a low carb, high fat diet.

Research also suggests that ketosis can lead to a decreased risk of heart disease. Low carb diets have also been proven helpful in cases of metabolic syndrome, type II diabetes, insulin resistance, and potentially various forms of cancer, polycystic ovary syndrome, and nervous system and neurodegenerative diseases such as Parkinson’s, Lou Gehrig’s (ALS), and Alzheimer’s disease.

Fans of ketosis often also cite the improved cognitive function and energy levels that comes from it.

Side Effects of Ketosis

As you might imagine of such a radical eating plan, there are some common side effects associated with ketosis.

Most of the side effects will come into play over the first week or so. This is often referred to as ‘keto flu’. This isn’t any kind of single condition, but rather refers to a group of symptoms that are likely due to sugar and carbohydrate withdrawal or changes to your gut bacteria and immune function as your body adjusts to using ketones for energy.

Signs of keto flu include headache, fatigue and brain fog, irritability and mood swings, nausea, stomach ache, and constipation, trouble sleeping (insomnia), sugar cravings, cramps, muscular fatigue and soreness, and bad breath.

Breastfeeding women should consider forgoing a ketogenic diet as it may affect lactation and milk supply.

Staying hydrated, especially using added electrolytes, can help with most of these symptoms. Many of these symptoms can also be mitigated by common ketosis supplements.

Ketogenic supplementation

There are plenty of supplements that can help you achieve ketosis faster, skipping that first week or two of bodily adjustment, whilst mitigating the symptoms of keto flu – KetoCharge is one such supplement.

Common ketogenic supplements include:


MCTs (or medium-chain triglycerides) are very high quality fatty oils derived from coconuts. You can take it by spoon, stirred into coffee, or mixed into shakes or smoothies. It is easily digestible, leading to little to no cramps or bloating.

Aside from being a good quality fat, MCT oil can aid with satiation whilst also boosting cognitive output. They can boost energy levels whilst helping to keep you in ketosis.

Omega 3

High-quality fat sources are always a good idea on a ketogenic diet. Much as MCT oil can be effective for ketosis, so too can omega 3 fatty acids. Cod or krill oil are both good options. Both are rich in DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid).

Both have been shown to aid in lowering inflammation and diminishing the risk of heart disease. They can also help in decreasing insulin and inflammatory markers.


We all need electrolytes. In fact, if you take part in regular exercise and/or find yourself sweating a lot, they are probably a good addition to your supplement routing. However, keto diets can be particularly susceptible to dehydration and electrolyte deficiency as your body works through its glycogen stores and loses water.

Your kidneys will flush the water out, along with the electrolytes sodium, potassium, and magnesium. This can lead to many of the main keto flu symptoms – nausea, cramps, fatigue, and so on.

Exogenous ketones

You can take exogenous ketones – that is, ketones from an outside source to top up your body’s natural output. This can give you a good energy boost, can keep on top of cravings, and keep you in ketosis far more easily than going without.

In rapidly boosting your ketone levels, you can switch into ketosis far quicker. This can help you to circumnavigate keto flu, getting rid of symptoms after just a day or two of beginning your ketogenic diet.

Vitamin D

Finally, vitamin D is a great supplement for those looking to follow a ketogenic diet.

Both vitamins D2 and D3 are key to maintaining health.

Vitamin D3 is naturally produced in the skin. It is triggered by sunlight or UV, meaning that those living in darker, colder countries would do well to supplement it. On the other hand, vitamin D2 can be found in many plants, especially mushrooms, making a vegetable-rich diet a very good idea.

You won’t often miss out on vitamin D as part of a ketogenic diet, especially if you take your few carbs from mushrooms and get plenty of sunlight. However, there is still a good reason to supplement with it.

Many ketogenic eating plans will be low in calcium. Vitamin D comes into play across many bodily functions. This includes calcium absorption. As calcium can help in maintaining immune health, cellular growth, and decreasing inflammation.

Make the most of the calcium you do have in your diet by taking plenty of vitamin D.

Written by Kate Harrison

Kate is one of our nutrition experts at PathMed and is also one of our in-house writers. There is little that gets past Kate when it comes to nutrition and she has a wealth of experience when it comes to fat loss and supplementation around losing weight. She is thorough in her research and is a real advocate for living a healthy lifestyle.