How long does Ketosis take when fasting : All you need to know

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how to get into ketosis

Table of Contents

What is intermittent fasting?

Intermittent fasting is the process of feeding your body in timed phases whereby you ensure that there are long periods where you do not eat. Doing this, enables you body to get in to a fat-burning mode as well as numerous other health benefits.

What are the stages of fasting?

There are 5 stages that the body goes through when you are embarking on a fasting diet. These are as follows : 

Fasting and the Fed State

This is the state where we all begin from and it is highly likely the body will have been fed regularly.


Your body will be nourished and have a decent hormonal balance which will have been influenced by regular daily eating.


Key hormones such as insulin, ghrelin and leptin will be working in sync to maintain homeostasis and so ensuring that they balance the body.


The body’s average insulin levels will be cycling depending on the foods you ear, and blood glucose will also be going through peaks and troughs.


It is generally accepted that the fed state is intermittent in that as soon as you eat, the body begins the process of being fed, digesting food and ensuring that the process repeats.


Fasting and the Early State

Your body will usually enter the early stages of fasting around 4 hours after the last meal.


This early state usually lasts for around 20 hours and it is during this phase that your body will see a decrease in blood glucose and blood insulin.


Once your body uses up the glycogen in the liver (for energy) it will then begin to seek another energy source. As your body realises that blood glucose is running out it will then increase a process known as lipolysis which is the process by which triglycerides from your fat cells get broken down and used as a fuel source.


It is also worth being aware that amino acids from muscle tissue can also be broken down to then be converted into energy. This is not a preferred option but can and does happen.


The Fasting State

This is the state we want the body to be in and it can last from 20 hours to the end of the fast.


Your body in this phase has no liver glycogen, is using ketones for fuel (by breaking down body fat) and may intermittently break down protein for energy.


We can say that now your body is in a state of ketosis which is essentially the process where your body is using your body fat as a source of fuel.


Measurable ketosis usually occurs 36 hours into the fast (by measurable we mean using ketostix). The most common tell-tale signs that you are in ketosis include fruity-smelling breath, weight loss, reduced hunger, and off-yellow colour urine.


The Prolonged Fasting State

Anything over 72 hours of fasting can be classed as a prolonged fasting state and as such your body will be in deep ketosis and also use over 95% of body fat for fuel (therefore increasing blood ketone levels).


Your Brain does prefer glucose to function and so the vital organ; your kidneys will manufacture glucose via gluconeogenesis. However, it is worth knowing that the brain can also use ketones as a fuel source.


The Break-Fast Fasting State

If you have been on a prolonged fast then your body will be operating like a well-oiled machine in terms of fat loss and overall weight loss. However, every fast has its day and eventually, you will want to break the fast.


To do this, you must follow a process whereby you do not supply the body with huge amounts of fats, carbohydrates and protein in a short period of time.


It is recommended that you break your fast with some light soup and even some fruit such as watermelon etc. You then build up to eating more over the course of 2 to 5 days depending on your fast duration.


Recommended Read: >>> Intermittent Fasting Guide <<<

Frequently Asked Questions : How long does ketosis take when fasting?

How long does it take to get into Ketosis?

Ketosis will occur within 72 hours once you either cease food OR follow a high fat, medium protein and low carbohydrate diet (less then 50g per day).

You can speed up ketosis by reducing the stored muscle glycogen and liver glycogen by performing exercises in the first 48 hours

What is the difference between ketosis and the ketogenic diet?

Ketosis is the process that occurs when you fast or consume higher fats and minimal carbohydrates. Eventually, the body changes its fuel source and breaks down fat which converts to ketones.


A ketogenic diet is a plan where you eat over 75% of your calories from good fats with some protein and ensure you have less than 50grams of carbohydrate per day. This plan then enables you to get into ketosis over 3 to 5 days.


What is the difference between intermittent fasting and ketosis?

Intermittent fasting is the style of diet whereas ketosis is the process of breaking down fats to ketones.

Do I need a blood ketone meter to measure blood ketone levels?

No, you can use ketostix that work via applying urine on the end and observing the changes in colour.

What happens to the fatty acids in my body as the fat breaks down?

As part of burning fat and reducing fat stores; as soon as you reach ketosis the body will convert them to ketones and then fuel majority of the body so it can sustain itself.

What happens to excess glucose?

As soon as you reduce the body’s glycogen stores, you will be primed to enter ketosis and begin to burn fat. Over prolonged periods, you body will boost ketone levels as the body converts fat to blood ketones.

Can I use exercise to trigger ketosis?

High fat ketogenic dieting and exercise can prove beneficial for ketogenic diets as it allows your body to decrease stored glucose (glycogen)

Recommended Read: >>> How Many Km Should I Run A Day To Lose Weight: An Essential Guide <<<

Are all low carb diets ketosis inducing?

No, low carb diets differ and the moment you go over 75grams of carbs per day, it is highly unlikely the body will enter ketosis.

How much fat intake should I have for a ketogenic diet?

You should keep fat intake to over 70% of your daily intake to promote your body in producing ketones. The moment your glycogen stores empty, the body will increase ketones

What are ketone supplements?

Ketone supplements should be limited as part of the high fat diet. They provide limited benefit and are known as exogenous ketones (externally supplied and naturally produced).

Will I reduce my insulin resistance in ketosis or ketogenic diet?

Yes, as part of the ketosis diet, the body will limit any insulin release as there will be minimal dietary carbohydrates. Once you restrict carb intake, and increase dietary fat your body will be forced to use stored fat.

How long does ketosis take when fasting?

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