Ketosis is a natural metabolic state.

It involves the body producing ketone bodies out of fat and using them for energy instead of carbs. You can get into ketosis by following a very low carb, high fat ketogenic diet (1).

A ketogenic diet can help you lose weight. In the short term, you can lose weight quickly, because it reduces the body’s stores of glycogen and water.

In the long term, it can suppress your appetite leading to a lower calorie intake.

As well as contributing to weight loss, ketosis may have several health benefits, such as reduced seizures in children with epilepsy (2).

Ketosis is quite complex, but this article explains what it is and how it can benefit you.

Ketosis is a metabolic state in which there’s a high concentration of ketones in the blood. This happens when fat provides most of the fuel for the body, and there’s limited access to glucose. Glucose (blood sugar) is the preferred fuel source for many cells in the body.

Ketosis is most often associated with ketogenic and very low carb diets. It also happens during pregnancy, infancy, fasting and starvation (3, 4, 5, 6).

For ketosis to start, you generally need to eat fewer than 50 grams of carbs per day and sometimes as little as 20 grams per day. However, the exact carb intake that will cause ketosis varies between individuals.

To do this, you may need to remove certain food items from your diet, such as:

  • grains
  • candy
  • sugary soft drinks

You also have to cut back on:

  • legumes
  • potatoes
  • fruit

When eating a very low carb diet, levels of the hormone insulin go down and fatty acids are released from body fat stores in large amounts.

Many of these fatty acids are transported to the liver, where they’re oxidized and turned into ketones (or ketone bodies). These molecules can provide energy for the body.

Unlike fatty acids, ketones can cross the blood-brain barrier and provide energy for the brain in the absence of glucose.


Ketosis is a metabolic state where ketones become an important source of energy for the body and brain. This happens when carb intake and insulin levels are low.

It’s a common misunderstanding that the brain doesn’t function without dietary carbs.

It’s true that glucose is preferred and that some cells in the brain can only use glucose for fuel.

However, a large portion of your brain can also use ketones for energy, such as during starvation or when your diet is low in carbs (7).

In fact, after only three days of starvation, the brain gets 25% of its energy from ketones. During long-term starvation, this number rises to around 60% (8, 9).

In addition, your body can use protein or other molecules to produce the glucose the brain still requires during ketosis. This process is called gluconeogenesis.

Ketosis and gluconeogenesis are perfectly capable of fulfilling the brain’s energy needs.

Here is more info about ketogenic diets and the brain: How Low-Carb and Ketogenic Diets Boost Brain Health.


When the brain isn’t getting enough glucose, it can use ketones for energy. The glucose it still needs can be produced from protein or other sources.

People often confuse ketosis and ketoacidosis.

While ketosis is part of normal metabolism, ketoacidosis is a dangerous metabolic condition that can be fatal if left untreated.

In ketoacidosis, the bloodstream is flooded with extremely high levels of glucose (blood sugar) and ketones.

When this happens, the blood becomes acidic, which is seriously harmful.

Ketoacidosis is most often associated with uncontrolled type 1 diabetes. It may also occur in people with type 2 diabetes, although this is less common (10).

In addition, severe alcohol abuse may lead to ketoacidosis (11).


Ketosis is a natural metabolic state, while ketoacidosis is a serious medical condition most often seen in type 1 diabetes that’s not well managed.

Epilepsy is a brain disorder characterized by recurring seizures.

It’s a very common neurological condition, affecting around 70 million people worldwide (12).

Most people with epilepsy use anti-seizure medications to help manage seizures. However, around 30% of people continue to have seizures despite using these medications (13).

In the early 1920s, the ketogenic diet was introduced as a treatment for epilepsy in people who don’t respond to drug treatment (14).

It has primarily been used in children, with some studies showing benefits. Many children with epilepsy have seen significant reductions in seizures while following a ketogenic diet, and some have seen complete remission (15, 16, 17, 18).


Ketogenic diets can effectively reduce epileptic seizures, especially in epileptic children who don’t respond to conventional treatment.

The ketogenic diet is a popular weight loss diet, and research has shown it can be effective (19).

Some studies have found that ketogenic diets are more helpful for weight loss than low fat diets (20, 21, 22).

One study reported 2.2 times more weight loss for people on a ketogenic diet, compared to those on a low fat, calorie restricted diet (23).

What’s more, people tend to feel less hungry and more full on a ketogenic diet, which is attributed to ketosis. For this reason, it is generally not necessary to count calories on this diet (24, 25).

However, it’s widely recognized that adherence to a diet is critical for long-term success. Some individuals may find it easy to adhere to the ketogenic diet, while others may find it unsustainable.

Some research suggests that the keto diet may not be the best way to lose weight. The authors of a 2019 review concluded that it was not better than other diets at helping people lose weight, and it may not have specific advantages for people with metabolic disorder (26).

More details here: A Ketogenic Diet to Lose Weight and Fight Disease.


Some studies show that ketogenic diets lead to more weight loss than low fat diets. In addition, people feel less hungry and more full.

Some scientists have suggested that ketosis and ketogenic diets may have other therapeutic effects, although it’s worth noting that not all experts agree on this (27, 26).

  • Heart disease: Some older studies suggest that reducing carbs to achieve ketosis may improve heart disease risk factors such as blood triglycerides, total cholesterol, and HDL cholesterol. However, a 2019 review notes that people on a very low carb diet may miss out on heart-healthy foods, such as whole grains and pulses (26, 28, 29).
  • Type 2 diabetes: The diet may improve insulin sensitivity and various risk factors that can lead to type 2 diabetes, including obesity (30, 31, 32).
  • Parkinson’s disease: A small study found that symptoms of Parkinson’s disease improved after 28 days on a ketogenic diet (33).

Ketosis and ketogenic diets may help with a number of chronic diseases.

While a ketogenic diet can have benefits for health and weight loss, it can also trigger some side effects.

Short-term effects include headache, fatigue, constipation, high cholesterol levels, and bad breath (34, 35), but these usually disappear within a few days or weeks of starting the diet.

Also, there may be a risk of developing kidney stones (36, 37, 38).

While breastfeeding, some women have developed ketoacidosis, possibly due to a low carb or ketogenic diet (39, 40, 41).

People who are taking blood sugar lowering drugs should consult with a doctor before trying a ketogenic diet, because the diet may reduce the need for medication.

Sometimes ketogenic diets are low in fiber. For this reason, it’s a good idea to make sure to eat plenty of high fiber, low carb vegetables.

The following tips can help you stay healthy during ketosis (42):

  • Drink plenty of fluids, particularly water.
  • Talk to your doctor before starting the diet and follow their advice.
  • Monitor your kidney function while following the diet.
  • Seek help if you have concerns about negative effects.

Ketosis may be beneficial for some people, but you should ask your doctor before switching to a very low carb diet, in case it’s not suitable for you.


Ketosis is safe for most people. However, some people may experience side effects, including bad breath, headaches, and constipation.

Ketosis is a natural metabolic state that can be achieved by following a ketogenic diet.

It may have a variety of health benefits, including:

However, following a strict diet to induce ketosis can be very difficult, and there may be some negative side effects. In addition, not all researchers agree that a keto diet is the best way to lose weight.

Ketosis is not for everyone, but it can benefit some people.

You can find even more info about the ketogenic diet on this page: The Ketogenic Diet 101: A Detailed Beginner’s Guide.

More about ketosis: