Fat Fasting 101: Everything You Need to Know

Fat fasting, sometimes called keto fat fasting, is a popular dieting technique that’s most commonly used by people who want to break through weight-loss plateaus or get back into ketosis after a cheat day.

It involves eating more dietary fat and fewer carbs than you typically would while maintaining higher-than-usual blood levels of molecules called ketones.

Fat fasting has recently gained popularity among people looking for a quick fix to their weight loss woes.

They believe it can help them drop pounds quickly without hunger pangs or cravings, which is typically not possible with traditional dieting approaches.

There is also an increasing number of people who are adopting fat fasting to kick-start ketosis before following a ketogenic diet and supplement their regular low-carb diets.

This article will look at what fat fasting is and whether it’s safe for you to try.

We’ll also take a quick look at some studies that have been done on the subject. So please keep reading to learn more about this dieting technique and find out whether it’s safe for you.

What Is Fat Fast?

Fat fasting is different from traditional fasts as you are not going without fat. This can be confusing at first.

Fat fasting, or keto fat fast as it’s sometimes called, is a diet technique that significantly increases your dietary fat intake—while also lowering your carb intake—to kick-start ketosis.

So, you’re not actually removing fat from your diet. You’re increasing it.

Ketosis refers to the situation where your liver is filled with fatty acids thanks to reduced carb intake and increased fat intake.

These fatty acids then break down into molecules called ketones, which are used for energy instead of glucose. That’s why being in ketosis is sometimes referred to as being “fat-adapted.”

When your body uses ketones for energy, you can say that you’re in what’s often called a state of “ketosis-adapted metabolism.”

Another phrase for this is “nutritional ketosis,” which refers to the situation where your body breaks down fatty acids into ketones using nutrients from food.

It’s different from ketoacidosis, a potentially dangerous metabolic condition that sometimes occurs in type 1 diabetics (1).

When you follow a fat fast, the main difference between your typical diet and your fat fast is that you dramatically increase the amount of dietary fat that you eat while also reducing your carb intake.

In turn, this causes a greater buildup of ketones in your body.

Most people who practice fat fasting will usually follow it for anywhere between 1 and 5 days. Some people even choose to do a 10- or 14-day fast occasionally.

While on the diet, you can have some protein in your diet, but most people find it best to stick with foods that are high in fat and low in protein.

What Do You Eat On A Fat Fast?

A fat fast involves eating a very low-carb, high-fat (LCHF) diet for anywhere from 2-14 days.

The aim is to keep your carb intake below 20 grams per day and increase the amount of fat you eat so that at least 80-90 percent of your daily calorie intake comes from fat.

However, not all types of fat are created equal. It would be best to eat saturated fats that come from animal foods and healthy plant oils like coconut oil, olive oil, avocado oil, and walnut oil.

It’s best to stay away from processed polyunsaturated fats like vegetable oils and margarine. They may help with weight loss in the short term, but long-term research suggests that they may increase your risk of heart problems.

Instead, eat plenty of healthy foods like grass-fed beef, pastured eggs, coconut oil, and olive oil.

You can also try adding some MCT oil to your diet. This is a type of plant-based fat that converts very easily into ketones (2).

A ketogenic diet, such as the one on which you’ll be following for your fast, typically provides anywhere from 60% to 80% of its calories from fat.

So with your fat fast, you’ll be eating somewhere around 80-90% of your daily calories from dietary fat.

To help you get an idea of what that looks like in terms of real foods, here an example day:

Breakfast: Fried eggs with butter and coconut oil

Lunch: Salmon with olive oil and butter

Dinner: Grass-fed steak with avocado oil and butter

Snacks: Avocado slices with olive oil, raw nuts, fatty meatballs fried in coconut oil/butter, grass-fed beef jerky.

Why Do People Use A Fat Fast?

There are a few reasons why people use the fat fast.

First of all, it’s an effective way to kick-start ketosis—the state where your body burns fat instead of carbohydrates for energy. More specifically, there are three main reasons why people do this:

  1. To lower insulin levels after you overeat on carbs (3).
  2. To quickly eliminate excess water to help you feel more energized and shed those last few pounds (4).
  3. To give your digestive system a little break from digesting large amounts of fiber along with other carbohydrates.

If you’re trying to lose weight, using the fat fast can help you on your journey. It can also be a great way to break through weight-loss plateaus that have kept you from reaching your goals.

The fat fast will reduce body fat, especially if it’s done alongside regular exercise and overall healthy nutrition.

By following a low-carbohydrate diet, your body will burn fat instead of carbohydrates for fuel.

Are There Any Risks?

It’s worth remembering that fat fasts should only be followed periodically and not as a permanent diet.

Some people may find that they start feeling light-headed or nauseous when following a fat fast, especially if they’re not used to eating so many high-fat foods.

In some cases, this may be caused by the buildup of ketones in your body.

However, if you keep eating a healthy low-carb diet after you fast, the symptoms shouldn’t last for long. However, if they persist or get too severe, it may be worth checking in with your doctor.

If your body starts making more ketones than it needs to, the excess ketones in your blood can build up and cause a condition called “ketoacidosis.” This happens when your body starts to break down fats to get energy, releasing excessive ketones into the blood.

Who Should Do A Fat Fast?

A Fat Fast should only be followed for a few days at most. This is because it can cause side effects like poor sleep, brain fog, low energy levels, dry skin, and bad breath.

If you have diabetes or are on medication, you shouldn’t do a fat fast without first discussing it with your doctor.

That said, the diet can be beneficial for some people. For example, some athletes may enjoy using a fat fast to help them get into ketosis quickly.

This is because it allows your body to rapidly use up its glycogen stores and start burning fat instead.

Additionally, if you’re trying to lose weight quickly or break through a weight loss plateau, a fat fast could help kick start your weight loss.

The diet may also be useful for people who struggle to get into ketosis despite following a low-carb diet and exercising regularly.

This is because it can rapidly lower your insulin levels and put you into ketosis within 24 hours.


Fat fasting is a type of diet where you eat less than 20 grams of carbohydrates per day for 2 days to 1-2 weeks.

It can help with weight loss, autoimmune disorders, and psoriasis. However, you may experience side effects like bad breath, dry skin, brain fog, and low energy levels.

It’s not recommended for people with diabetes, and you should speak to your doctor before following the diet if you have any medical conditions.

Categorized as Diet

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