Keto Diet: How Long Should You Fast?

The ketogenic diet is a high-fat, low-carbohydrate diet that has been around since the 1920s. It was originally used to help treat epilepsy and diabetes, but in recent years it has gained popularity as a weight loss method. The keto diet involves drastically reducing your carbohydrate intake and replacing it with fat. This puts your body into a metabolic state called ketosis, which can lead to weight loss and improved health. However, the keto diet is very restrictive and may not be suitable for everyone. It can also be difficult to follow due to the limited food options. There are several types of keto diets, including the standard ketogenic diet, cyclical ketogenic diet, targeted ketogenic diet, and high-protein ketogenic diet. The length of time you should follow the keto diet depends on your individual goals and health status. Some people use it as a short-term dietary change to jump-start weight loss, while others follow it as a permanent lifestyle. It's important to speak to a doctor or nutritionist before starting the keto diet to ensure it is safe and appropriate for you.

Intermittent fasting and keto can be combined

How Intermittent Fasting Works

Intermittent fasting (IF) is a diet approach in which you plan specific times when you are not eating. There are several ways to do it, including the popular 5:2 IF, where five days are normal eating and two are extremely low-calorie (around 500) fast days. Other plans involve not eating for a 24-hour period, or time-restricted eating, such as eating for 8 hours and fasting for 16 each day.

How Keto Works

The ketogenic (keto) diet is a high-fat, very low-carb way of eating. Carbs are typically reduced to 20 to 50 grams per day, which forces your body to rely on fats instead of glucose for its main energy source. This metabolic process is called ketosis.

Combining the Two

Combining the two diets gained popularity when intermittent fasting expert Jason Fung, MD, author of *The Obesity Code*, recommended using keto as a foundation with fasting. This combination may help your body reach ketosis quicker than the keto diet alone.

However, there is a lack of rigorous research on this combined approach, and it hasn’t been proven to work for weight loss. Experts say it could make sense, though the lack of research means you may want to think twice before trying it.

Who Should Try It?

Anyone who has been on keto for more than two weeks and would like to add IF may do so — with the okay from their healthcare team. Notably, it may not be appropriate for people who are following keto as part of a plan to address prediabetes or diabetes. It is also not recommended for people with chronic kidney disease, a history of eating disorders, those undergoing active cancer treatment, or those who are pregnant or breastfeeding.

How to Start

Practitioners at the Cleveland Clinic do not advise people to start both keto and IF at the same time. Instead, people start with keto, then after being on the diet for a couple of weeks to months, they might consider adding IF. For their patients, they suggest a 12- to 16-hour fast. For many people, not eating for 12 hours a day (e.g., overnight from 7 p.m. to 7 a.m.) is a natural habit anyway and doesn’t require skipping meals.

Possible Health Benefits

There is very little research on the health effects of doing keto and IF together, but it’s clear that ketone levels increase when the plans are combined. This may help accelerate weight loss, but everyone responds differently.

Possible Health Risks

As for long-term risks, people with seizure disorders (what keto was developed to treat) have been on the ketogenic diet for decades and demonstrate excellent health. However, like any diet, it all depends on what foods you’re eating. A keto diet rich in bacon and butter is different from one rich in avocado and olive oil, and poorly planned keto can lead to nutritional deficiencies.

Because adding IF may make you cut calories too drastically, you may also lose too much weight or lean mass (muscle) if you take the restriction to the extreme. To maintain muscle mass, it is recommended to consume 1 gram per kilogram of body weight in protein every day.

Intermittent fasting can help with weight loss

Intermittent fasting is an eating pattern that involves rotating between periods of fasting and normal eating. It is not a diet in itself, as it does not specify what foods to eat, but rather when to eat them. This approach can be used in conjunction with other diets, such as the keto diet, to enhance their effects.

Intermittent fasting is a popular weight loss technique. Studies have shown that it can naturally restrict calorie intake and appetite, leading to weight loss. It also works on a hormonal level by increasing the production of norepinephrine, a fat-burning hormone. This hormonal shift can increase the body's resting metabolic rate, allowing for more efficient calorie burning.

In addition to weight loss, intermittent fasting has been shown to have several health benefits. It can help reduce insulin and blood sugar levels, improve cardiovascular health, and reduce the risk of certain diseases. For example, it may lower the risk of heart disease by reducing cholesterol and blood pressure. Intermittent fasting has also been linked to improved brain function, reduced inflammation, and better blood sugar control.

There are several different intermittent fasting routines, such as the 5:2 method, the 16/8 method, and alternate-day fasting. The 16/8 method, for instance, involves eating during an eight-hour window and fasting for the remaining 16 hours of the day. The 5:2 method involves eating normally for five days and restricting calories to 500-600 for the remaining two days.

While intermittent fasting has many potential benefits, it may not be suitable for everyone. It is important to consult with a healthcare professional before starting any new diet or eating pattern, especially for those with certain health conditions or for pregnant or breastfeeding women. Additionally, it is important to maintain a healthy and well-rounded diet during the eating periods to ensure adequate nutrition.

Intermittent fasting has other health benefits

Intermittent fasting has become one of the most popular dieting trends in recent years. It involves eating within a specific time window and fasting for the remainder of the day. For example, the 16:8 method involves eating during an eight-hour window and fasting for the remaining 16 hours.

The approach is mainly used as a weight-loss technique, but it has been shown to have other health benefits, including:

Improved Brain Function

Intermittent fasting has been shown to improve brain function and boost memory. Animal research has also shown that it may increase the growth of new nerve cells, which could benefit brain function.

Reduced Risk of Type 2 Diabetes

Intermittent fasting can reduce insulin resistance and lower blood sugar levels, which are major features of type 2 diabetes. Weight loss is also a key factor in preventing the development of type 2 diabetes, and intermittent fasting is an effective weight-loss method.

Improved Heart Health

Intermittent fasting has been shown to improve several risk factors for heart disease, including blood pressure, cholesterol levels, and inflammatory markers. It can also lead to a decrease in triglycerides, a type of fat in the blood linked to heart disease.

Reduced Inflammation and Oxidative Stress

Oxidative stress is a factor that contributes to ageing and chronic diseases. Intermittent fasting has been shown to enhance the body's resistance to oxidative stress and reduce inflammation, which plays a role in various conditions.

Cellular Repair

Fasting triggers a process called autophagy, which is a cellular waste removal process. This process may provide protection against several diseases, including cancer and neurodegenerative diseases such as Alzheimer's.

Fasting for 12 hours can kickstart ketosis

Fasting for 12 hours is a great way to kickstart ketosis. Ketosis is a metabolic state in which the body burns stored fat for fuel instead of glucose. This can be achieved by reducing carbohydrate intake and increasing physical activity. Intermittent fasting is a popular way to reach ketosis, as it involves timing your food intake to improve overall health and boost weight loss.

Intermittent Fasting and Ketogenic Diet

The ketogenic diet, or keto, is a high-fat, moderate-protein, and very low-carb diet. When combined with intermittent fasting, this approach can help with weight loss and improve results. Intermittent fasting involves eating only during a certain time window, such as 8 hours, and then fasting for the remaining 16 hours. This can be done daily or on alternate days.

Benefits of Intermittent Fasting

Intermittent fasting has been shown to promote weight loss and reduce risk factors linked to heart disease, including diabetes, high blood pressure, unhealthy blood lipid levels, and inflammation. It can also help people realise how many calories are in certain foods, making it easier to choose lower-calorie options. Additionally, intermittent fasting triggers the same fat-burning process as a low-carb or keto diet, making it a healthier option.

Getting into Ketosis

Reaching ketosis can be challenging and may take a few days to a week or more. Fasting for 12 hours is the fastest way to get into ketosis, as it quickly depletes glycogen reserves. Medium-chain triglyceride (MCT) oil supplements may also help speed up the process. However, it is important to note that ketosis is not safe for everyone, especially those with type 1 diabetes, and should be done under medical supervision.

Sample Menu for Intermittent Fasting and Keto

A typical day on an intermittent fasting and keto plan might include black coffee and scrambled eggs with avocado slices for breakfast, a large leafy green salad with grilled salmon for lunch, and chicken leg with wild rice and zucchini for dinner. It is important to work with a registered dietitian to determine the right ratios of carbs, protein, and fat for your individual needs.

Fasting for 24 hours or more has additional benefits

Fasting for 24 hours or more has been shown to have additional benefits on top of the advantages of shorter fasts. One of the main benefits of longer fasts is that they can help to activate ketosis, a metabolic process where the body burns stored fat for energy instead of glucose. This is because longer fasts can help to increase ketone levels in the body, which are derived from fat breakdown in the liver.

Another benefit of fasting for 24 hours or more is that it can help to improve insulin sensitivity and lower blood sugar levels. This is because during a fast, insulin levels and glycogen stores decrease, which leads to a reduction in blood sugar levels. This can be especially beneficial for people with type 2 diabetes or prediabetes.

Longer fasts have also been found to boost the self-cleaning process in the body known as autophagy. Autophagy involves the removal of invading microorganisms and toxic compounds, as well as the recycling of damaged proteins. This process is thought to play an important role in stopping the aging process, reversing disease, and preventing cancer.

In addition, fasting for 24 hours or more can help to simplify your keto meal plan and make weight loss easier to maintain. This is because it can be challenging to gain weight when following a fasting regimen, and it also removes the need for frequent meal prep and planning.

Finally, longer fasts can help to boost overall fitness results. This is because fasting while training can lead to higher metabolic adaptations, improved muscle synthesis, and an improved response to post-workout meals. Studies have shown that there is no effect on performance in training while fasting.

Frequently asked questions