What is a fat fast and should I do it?
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Fasting is a powerful tool to decrease your insulin levels and to regain good insulin signaling very quickly; in this sense it’s even more efficient than the ketogenic diet., There are big benefits to be had with it, especially if you wish to control your blood sugars or lose fat.
A fat fast is a compromise from typical fasting. It’s as close as you can get to fasting without actually fasting.
What’s a fat fast?
It’s simple: during a water fast you drink only water, during a fat fast, you consume just fat. That would be the strict definition. But even on water fast you can drink black coffee, tea and, bone broth.
It basically comes out of doctors wanting their patients who fail to fast to still get some of the benefits from – so they compromise with a fat fast.
The very low-calorie meals in practice don’t just contain fat. The main reason for this is because no foods (besides oils) consist of 100% fat. Drinking oil (not even the holy extra virgin olive oil) is not something we recommend.
So if you’re finding typical fasting too hard, we suggest trying a fat fast where you eat foods that contain only a little bit of protein (and negligible amounts of carbs). You should aim for 80-90% of calories from fat and the rest from protein.
More details on what that looks like in practice below.
The traditional fat fast go back to Dr. Atkins and is high fat, low-calorie diet that involves 4-5 small meals and 1,000 -1,200 kcals per day. At Nutrita we don’t believe in calorie counting as a good way to control body composition and metabolism. We always recommend to eat until full even though this can vary quite a bit from person to person. Hence this modified version of the original fat fast we recommend people can try out if they’re failing to do a typical fast at first.
Fat fasting is like an extreme version of the ketogenic diet. You keep the carbs around zero and ramp up the fat like crazy and protein is kept relatively low. You might even abstain from lean meats entirely.
Carbs considerably raise insulin levels and even protein has an impact. Fat is the only macronutrient that has a tiny effect on raising insulin levels above fasting (basal) ones. This is why a fat fast allows you to keep your insulin extremely low despite eating.
What are the benefits of fat fasting?
Fat fasting gets you into ketosis quickly and deeply, not too different than with typical with. Because fat is very satiating, it suppresses your appetite. Being in ketosis also suppresses appetite, and fat fasting gets you even deeper into ketosis.
Ketosis is known as a state where you very efficiently use fat for fuel. So, on a fat fast, you maximize fat burning and maximally decrease your appetite. That’s an incredibly powerful combination for weight loss!
Fat fasting, like regular fasting, is a temporary, intermittent strategy. You can also think of it as a means to an end, or a useful signpost telling you how normal your appetite is. Intermittent fasting can also be thought of as the pattern of eating people naturally fall into when eating about twice a day, on average.
There are three good reasons to do a fat fast:
1 – A stepping stone to typical fasting
When fasting, most people are very hungry during the first two days. On day three, when glycogen stores are emptied, the body is forced to burn body fat as fuel. As most people have plenty of energy stored as fat, there is no energy shortage as soon as the fat stores are accessible. This is precisely the reason why you don’t feel hungry when fasting.
Insulin is the primary hormone that suppresses fat burning or lipolysis. Because you bring down your insulin levels on a fat fast, you optimize fat burning. Once your body is used to burning fat as fuel, it will also burn body fat more efficiently.
Fat is fat, and burning fat from the diet or body fat does not make a big difference. The only difference is accessibility. So a fat fast helps will help some people to bypass these first 2-3 days on a water fast, where you may reach peak hunger.
2 – Overcome a weight loss plateau
Many people initially lose a lot of weight when starting a ketogenic diet and then hit a weight loss plateau. Because the fat fast fat is even better for fat burning than a regular ketogenic diet, and at the same time decreases appetite and hunger, it helps you to overcome a plateau.
For more information on how to leave behind such a plateau, check out our keto plateau post.
3 – Extreme hunger pangs and carb cravings
Most people feel less hungry on a ketogenic diet, and carb cravings tend to disappear very soon. However, everybody is different, and for some, this effect is less pronounced. Or it just takes longer.
In this case, fat fast is an option for overcoming this hurdle and starting to get some of the benefits from ketosis. So, a fat fast can be seen as a faster method than gradually reducing one’s carb intake. Or, a slower method than straight fasting to get into ketosis.
Other people find it easier to decrease their carb intake gradually. For more information about how to start the ketogenic and to get into ketosis, check out our Ultimate Keto Diet Guide for Beginners.
What does science say about fat fasting?
The biggest fear with fasting is always losing valuable muscle protein. Because it’s such hard work to build up muscle mass, the last thing you want to do is to put it at risk through fasting. Thankfully, fasting shouldn’t be of much concern.
First of all, fasting shouldn’t be confused with a calorie-restricted diet; these all too often restrict high-quality animal protein excessively. Yes, technically speaking fasting is calorie restriction put to an extreme. There are benefits from removing calories alone and you will likely take up fewer calories than you expend on a fat fast. So isn’t fasting offering just more of what calorie restricted diets do for you over the long run?
No! Calorie restriction means not eating despite being hungry. If you don’t eat because you are not hungry, your body does not feel energy deprived.
To sum it up: the big difference to conventional calorie restriction is that fasting makes fat stores accessible and as a consequence, energy expenditure goes up instead of down.
Your body only burns muscle protein in an emergency situation. Muscle protein is a precious resource, and your body is not as crazy to burn it as long as it has access to significant fat stores.
For this reason, a well-timed regular fast, fat fast or just a ketogenic diet allow you to rely on fat for energy as well as preserve your muscle mass. Furthermore, fasting triggers the release of growth hormones and the ketogenic diet is known to have a muscle-sparing effect in calorie-restricted scenarios,, So, the ketogenic diet in combination with fat fasting or regular fasting can be fine to preserve muscle mass while losing fat.
How to fat fast the right way?
The most important rule: don’t count calories on a fat fast – that would be totally crazy and self-sabotaging. The fat fast is the exact opposite of a low-calorie diet – with good reason.
After a few days on it, your appetite decreases and your calorie intake will automatically normalize. And it will give you the confidence of going about your day with way less food. It’s a useful way to kickstart yourself into water fasting.
When starting the fat fast, you may still eat quite frequently. But remember, the point is to overcome hunger pangs and worries about not eating, not to fully feed yourself as you usually would. Very soon hopefully you’ll notice that you feel full for longer.
Listening to your body at this point is crucial.Don’t eat because it’s time to eat. Don’t eat because it’s a habit. Don’t eat when you are not hungry.
A fat fast is not dangerous, but it’s meant to be short-term. For a few days, it gives you everything you need to get as close as possible to a typical full fast. If you use eggs for instance, they’re incredibly energy-dense food, so you certainly don’t have to worry about nutrient deficiencies.
But the macronutrient distribution is skewed extreme, and as your appetite diminishes dramatically your protein intake will drop. That’s fine for a few days, but remember this way of eating is not sustainable long-term – it’s to help get into typical fasting. Do a fat fast for a few days, or one-week maximum.
It is crucial that you only eat healthy fats on a fat fast. You want to do something good for your body, and don’t want to inflame yourself! In brief, avoid high omega-6 seed oils and have animal fats mainly, like butter or lard, but here’s our fat guide for more information.
To make it even easier for you: in the next section, you’ll find exactly what to eat on a fat fast.
What to eat on a fat fast
- Fatty fish (mackerel, herring, sardines, salmon)
- Butter, lard, ghee, olive oil, avocado oil, coconut oil, MCT oil
- Mayo (made from avocado oil)
- Lettuce and other leafy greens
As you can see, this list is very short and clear. As long as you stick to this list, there’s not much room for errors.
In case you need some inspiration, you find some easy recipes and a 3-day meal plan below.
- 3 eggs or more
- Salt and pepper
- A few leaves fresh basil
- 1 tablespoon of butter
Melt the butter in a pan on medium heat. Whisk the eggs and the remaining ingredients, and in the pan until your preferred texture is reached.
Optional: add some fried bacon as a side.
Alternative: fried eggs, poached eggs, boiled eggs…
Avocado oil is ideal for mayo because it contains healthy fats and, unlike olive oil, it does not have a strong taste of its own.
- 2 egg yolks
- 1 tablespoon of lemon juice
- 200 ml of avocado oil
- Salt & pepper
Whisk the yolks, ¼ teaspoon salt, and the lemon juice until combined well. Then start adding the avocado oil drop by drop while whisking constantly. After the first ½ cup of oil, you can add the oil in a slow, thin stream. The mayonnaise will be slightly yellow, thick and creamy.
Deviled eggs or egg salad
1 tablespoon mayo per egg
Boil the eggs for 4-6 minutes. For the deviled eggs, cut the eggs in half and spread with mayo. For the salad, cut the eggs into pieces and mix with the mayo.
Spinach with salmon
150 g fresh spinach, 250 g salmon
Salt, pepper & ground nutmeg, 1 tablespoon of butter
1 tablespoon of coconut oil
Melt the coconut oil in a pan on medium heat. Add the spinach, stir regularly and cook for about 5 minutes. Season with salt, pepper, and nutmeg.
Fry the salmon in a separate pan with the butter. Season with salt and pepper.
Optional: serve with sauce Hollandaise.
3-day meal plan
The 3-day meal plan is just an example to get you started. How many meals you eat per day and how much you eat totally depends on you and your hunger. Let your appetite guide you!
Scrambled egg with bacon
Salmon with spinach and sauce hollandaise
Green salad with avocado, olives and mayo dressing
Avocado mackerel salad
Green salad with olives, bacon, olive oil and 1 tablespoon lemon juice.
Salmon with spinach and fried bacon.
Green salad with olives, olive oil and 1 tablespoon lemon juice.
A fat fast is an excellent way to deepen ketosis, a large part of the benefit typical water fast provides. Fat fasting can be a good way for people to progress to a typical fast when struggling to make the transition. Fat fasting may also help you get rid of carb cravings. It is, however, a short-term method with a specific goal in mind.
Fat fasting is a temporary tool to help you get into typical water fast, and by its nature isn’t a balanced way of eating in a long-term perspective, For this reason, you may want to try it out for a few days, or a week maximum.
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Written by Sarah Neidler, PhD
Sarah Neidler did her PhD in cancer research at the Beatson Institute for Cancer Research in Glasgow. She has a strong interest in nutrition and the ketogenic diet and believes that they are beneficial for the treatment and prevention of chronic conditions, such as heart disease and diabetes. She loves cooking, reading, sewing, Yoga, and CrossFit.