Nutrition

What Is a Fat Fast? Pros, Cons and How to Do It

What Is a Fat Fast? Pros, Cons and How to Do It

Fat is finally getting its day in the sun. As a macronutrient that got a lot of flak from both health professionals and wellness enthusiasts for years, the tables have finally turned, and fat is being recognized for the health-promoting nutrient it is.

Some people are even using fat as a way to get the benefits of fasting without having to forgo food. Fat fasting, also known as a “keto fat fast,” is one of the latest trends hitting the wellness industry.

But is fat fasting for you? Read on to learn more.

What Is Fat Fasting?

While intermittent fasting (IF) has been taking the health and wellness industry by storm, another type of fast has emerged right behind it — fat fasting.

Unlike IF, when you fat fast, you're still allowed to consume calories, with the caveat that 80%-90% of them come from fat. And while you’re not restricted with “eating windows” or prolonged periods without food, calories do need to remain somewhere between 1,000 and 1,200 per day.

The basic rules of a fat fast are:

  • 1,000-1,200 calories per day (two or three small meals of around 250-400 calories each)
  • 80%-90% of all calories coming from fat
  • Maximum duration of two to five days

Basic rules of a fat fast - Infographic

If you’re wondering why fat fasts should only be followed for two to five days max, it’s because, frankly, it’s not a balanced and sustainable way to eat.

So why would you want fat fast in the first place?

Fat fasting can help you get into a state of ketosis, which research shows mimics many of the health benefits associated with calorie restriction, such as enhanced energy production, decreased inflammation, and improved brain health[*].

You can also use fat fasting as a way to break through a weight loss plateau.

How Does Fat Fasting Burn Body Fat?

The primary purpose of a fat fast is to get your body into a ketogenic state. When your body enters ketosis, it switches its preferred metabolic fuel from glucose to ketones, which are energy molecules that are broken down from fat in your body.

So how does eating fat get you into ketosis? Let’s break it down a bit.

When you consume a standard diet that contains carbohydrates, your body runs primarily on the broken-down form of carbs — glucose. Glucose can either come from the carbohydrates you eat or from your body’s glucose stores (which are limited).

carbs fat fast

As long as you keep consuming carbohydrates, your body has enough glucose to fuel your cells and store extra glucose for later. However, when you decide to switch things up and restrict carbs, something different happens.

In the absence of incoming glucose, your liver starts looking for new sources of fuel. In an effort to keep things running smoothly, it will first use up your glucose stores (also known as glycogen), and then it will start a process called gluconeogenesis (where your body makes glucose from other macronutrients).

But this effort can only take you so far; before long, your liver's ability to produce enough glucose internally will fall short, and the process of ketogenesis will begin.

Ketogenesis is the process of creating ketones, which are energy molecules that come from stored fat in your body. You always have the ability to produce ketones, but as long as glucose is available, your body will utilize that as a fuel first.

Why is this? Because glucose is more readily available as a fuel source.

It takes your body more energy to create ketones, and once ketones have become your primary fuel source, it can still take your body a few days to a few weeks to get used to this new type of fuel[*][*].

Ketosis and Fat Burning

Since being in a ketogenic state means that you’re tapping into your body's fat stores for energy, it would make sense that this type of eating would result in fat loss. However, your body is still going to use the calories you consume from food first before tapping into any stored energy.

With this in mind, even if you’re fat fasting, overeating or overconsuming calories will still prevent fat loss. That’s why fat fasting comes with a limit on daily caloric intake.

The main difference between fat fasting and true fasting (abstaining from food entirely) is that while both can get you into a state of ketosis, you can still eat food throughout the day when fat fasting.

Unfortunately, a protein fast wouldn’t have the same effect as a fat fast because even though it doesn’t provide as much glucose, it can still prevent the production of ketones due to the presence of the hormone insulin[*].

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