Ketosis: Definition & Keto Diet Effects

Ketosis is when the body produces ketone bodies from fat and uses them instead of carbs for energy. 

Since ketosis is a metabolic state that’s natural for your body, following a ketogenic diet high in fat can help as a tool for weight loss.

It’s possible to lose 5-10 pounds in the first week of starting the keto diet.

Your body flushes out mainly water within the first week and begins to deplete your glycogen stores. 

The ketogenic diet naturally leads to a caloric intake that’s less than normal because a diet high in fat tends to be more satiating.

There’s a lot that happens in ketosis, so read on to learn more about what it is, what it is not, and why it’s a necessary component of your weight loss journey with the keto diet.

What Is Ketosis?

When your body enters into a state of ketosis, your body produces ketones found in your blood in high concentrations. 

When you switch your fuel source to mainly fat, your body has to adapt to the food it’s being given.

Instead of using glucose for fuel, your body has to use ketones to maintain a healthy state of being.

Before starting any low-carb diets like keto, your body’s primary source of fuel is glucose, and that’s due to the carbs you eat.

Your body breaks down carbs into glucose which it stores and uses as energy.

To get into a state of ketosis, you should be consuming no more than 5% of your daily caloric intake from carbohydrates. 

Depending on where you’re starting from, that can be anywhere from 20-50 grams of carbs per day, but it should not exceed that.

The following foods must be eliminated from your diet, or you’ll never reach a level of ketosis for its fat-burning effects on the body.

Foods high in sugar like processed food, candy, sugary drinks, and even fruit. You’re basically eliminating sugar altogether.

Grains, legumes, and potatoes need to be eliminated as well.

When starting a ketogenic diet, a specific hormone in your body called insulin goes down.

When your levels of insulin drop, then your fat stores release fatty acids in high quantities.

These fatty acids make their way to your liver, where they oxidize into ketone bodies. These are the building blocks of your new energy source.

When these fatty acids convert into ketones, they can now provide energy for the brain and the body since ketones can pass through the blood-brain barrier. 

Triggers For Ketosis

Diets that follow a strict low-carb approach, like the ketogenic diet, will trigger ketosis to happen. 

When you consume fewer carbs, you’ll have less glucose in your body and blood. Your body then turns into a fat-burning machine since you’ll be using your fat stores for energy. 


Some people believe that the brain cannot function without glucose as your body’s fuel source, and that’s a common misconception. The brain functions very well in ketosis.

While it has been shown that specific brain cells can only utilize glucose for fuel, the overwhelming majority of your brain can use ketones as its energy supplier.

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. (1)


Gluconeogenesis is critical to know because this happens when new glucose molecules form in your body. 

This process is different from glucose breaking down from muscle glycogen and mostly takes place in your liver. The kidneys and small intestine also can do this to a smaller degree.

Not to be confused with glycolysis, which is the breakdown of glucose molecules.

Because of gluconeogenesis, your body can still produce the glucose it needs for the cells your brain requires. 

Gluconeogenesis and ketosis give your brain all the energy it needs to function optimally.

So when your brain doesn’t receive enough glucose from your diet, it switches over to ketones for energy from the high fat intake you’re consuming.  

Any additional glucose can be created from your body through natural processes or even protein.

Ketosis Vs Ketoacidosis

Although sounding similar, ketosis and ketoacidosis are not the same thing.

Ketoacidosis refers to diabetes type 1, and it’s very life-threatening for those with diabetes. 

It’s a combination of very high levels of ketones in the body and blood sugar levels.

This lethal combination causes the blood to be very acidic, which puts strain on internal organs like the kidneys and liver. 

Ketoacidosis can come on extremely quickly, sometimes within 24 hours, and needs to be treated immediately.

This occurs in patients with type 1 diabetes, where their bodies don’t produce the insulin they need. 

Ketosis Vs Ketogenesis

Allowing for an alternative fuel source for the body, Ketogenesis can produce ketone bodies through your body’s metabolic pathways. 

When you enter into ketosis, your ketone production by the body is increased.

Ketogenesis’s Molecular Structure

Through the breakdown of fatty acids, ketone bodies are produced. Acetone, acetoacetate, and beta-hydroxybutyrate (BHB) ketones are made. 

These ketones are made up of R-groups attaching to a carbonyl group. They are water-soluble molecules, but out of the three molecules, acetoacetate and BHB are acidic. 

Ketosis Weight Loss Effects

Studies have shown that the ketogenic diet is very popular because of its effects on weight loss in patients. (2)

There have also been follow-up studies to see the outcomes between the ketogenic diet and other low carb diets, and the keto diet has remained the clear winner reporting 2.2x more weight loss compared with other low-carb diets. (3, 4)

The patients reported feeling less hungry while on the keto diet, and this is due to the satiety you feel with higher fat foods.

Even though you may feel full on the diet, you should still track your calories consistently to make sure you stay in a caloric deficit. 

Sticking to the diet for the long term has been shown to give you the best results. 

How To Achieve Ketosis

If you’re having a hard time getting into ketosis, these tips will help:

  • Do not consume more than 50 grams of carbohydrates a day.
  • Track your intake of food. Know the breakdown of foods you’re consuming each day and how many calories you’re taking in through fitness apps like MyFitnessPal and others.
  • Consume similar meals each day to avoid not counting calories correctly.
  • Increase your intake of high-quality fatty foods. You should be getting around 70% of your calories from fat each day.
  • Try fasting. Short-term intermittent fasting has been shown to deplete glycogen stores, getting you closer to ketosis.
  • Exercise allows for you to burn through more glycogen as well. This, in combination with intermittent fasting, is a quick way to help you reach ketosis.
  • Test yourself. By testing your ketone levels you’ll know if you’ve reached a state of ketosis or not.

Symptoms Of Ketosis

Here are a few ways you can see if the keto diet is working for you. When you’re in ketosis, you’ll notice the following:

  1. Ketones. Taking your blood or using ketone strips can let you know if you’ve gotten into ketosis. An increased level of ketones is a surefire way to tell you you’re body is in ketosis.
  2. You’re losing weight. As you stick to your diet, you’ll notice the weight coming off each week as long as you’re following the rules of the keto diet and you’re not overconsuming calories or having cheat meals.
  3. Thirst levels. You may feel thirstier than usual, and this is a side effect of water loss. If you’re feeling dehydrated, make sure you’re consuming water. A good rule of thumb is to have at least half of your body weight in ounces.
  4. Muscle cramping. Dehydration will also lead to cramps. Because your electrolytes are lower than usual, this can lead to spasms. Make sure you’re getting enough calcium, magnesium, and potassium in your diet. Oh, and don’t forget the salt.
  5. Headaches. When switching to a ketogenic diet, it’s common to get keto headaches. These usually don’t last for longer than a week and are combined with other symptoms of the keto flu.
  6. Fatigue. Switching from carbohydrates, you may feel weaker than expected. This also should subside quickly once you’re fat-adapted and in a state of ketosis.
  7. Changes in sleep habits. Take notice if you’ve been having issues sleeping, as this can be caused by entering into ketosis. Like the other symptoms here, this only lasts for a short time.
  8. Bad breath. When you’re in ketosis, you’ll notice, or someone will tell you that you have bad breath. Acetone, which is a type of ketone, is the main factor for having smelly breath. Be sure to keep mints around and keep your mouth fresh with mouthwash to avoid funny stares. 
  9. Better focus. In the first week of adapting, you may find yourself with brain fog, but when you enter into ketosis, many people report having more clarity and focus than prior to being on the diet. 

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