This article has been Fact-Checked by Kendall Kennedy MS, RD, RYT
Fasting can be extremely good for your health. But there are different ways to do a fast. Each with its own advantages and disadvantages. Not every kind of fast may be right for you. It’s important to choose right.
There are two ways we can seperate different kinds of fasting. The first one is the time and frequency you will fast. The second one is by looking at what you will consume during your fast.
Choosing the right combination can greatly help you with losing weight by fasting.
Remember to consult with your doctor before you make any big changes to your lifestyle.
What will you eat while fasting?
What you can “eat” while fasting is determined by the kind of fast you will do. Each one has its advantages and disadvantages.
Water fasting
Water fasting is literally not consuming anything besides water for a period of time.
The advantage of water fasting is that you give your body complete rest. It doesn’t have to digest anything.
There are also some important disadvantages of water fasting. For starters, it makes the fasting process more difficult to stick to. Constantly tasting things has become a habit for a lot of people these days.
You might feel too restricted by only drinking water. This can make it so you don’t actually finish the fast.
The planned duration of your fast is important for your choice. Water fasting is not always the healthiest way to fast.
The human body is able to store an amount of vitamins and minerals. The thing is that some of these micronutrient stores don’t last that long. If you only drink water, there is no way to replenish these micronutrient stores while you fast.
Your body needs micronutrients to survive and thrive.
If your diet is good and your body healthy you can probably do a water fast for up to 24-48 hours safely. Any longer than that and a water fast might be bad for your health.
Calorie fasting
Calorie fasting is when you avoid eating calorie heavy foods. This comes down to eating low macro vegetables and vitamins and minerals. The plan is still to stay in a fasted state. Some vegetables contain such a small amount that this is still possible if you don’t overdo it.
You can also consume coffee and tea on a calorie fast if you don’t add any sugar or cream to it.
The advantage of calorie fasting is that you get a lot of fasting advantages while still replenishing the micronutrient stores in your body. This makes it a better option for extended fasts longer than 24-48 hours.
You will need some micronutrients more than others so you don’t have to be worried about all vitamins and minerals during extended fasts. For medium-extended fasts mostly electrolytes will be the problem. Long extended fasts should be done under supervision and with an airtight plan on what you will eat when.
A disadvantage from a calorie fast is that you still keep some parts of the digestion system busy.
How long will you fast?
Something else you’ll have to decide is how long you will fast. Again there are advantages and disadvantages to different kinds of durations.
Obviously the longer you fast, the more calories you will burn in body fat. However, you need to make more preparations to do longer fasts. Find out how long is right for you.
Time-restricted eating
Time restricted eating is implementing a shorter time window of eating each day.
Let’s say you have your first calories in the morning in the form of some cream in your coffee at 7 a.m. and you have your last bite of dessert at 9 p.m. Then your window of eating is 14 hours.
With time restricted feeding you try to make that window smaller. The greatest improvements can be seen by switching to an 8 hour time window. But some people shorten this even more for more benefits to one meal a day.
Some people still consume coffee and tea (without anything added) outside this time window, some don’t. You will see a small advantage by not doing this but it doesn’t make the biggest difference.
Time restricted eating is gaining in popularity and this has a reason. The more research is being done the more advantages of time restricted feeding are being discovered.
Advantages of time restricted eating
The unique thing about time restricted eating is that you can see great health increases by doing something that saves you time and effort.
You will have to prepare one meal less a day.
Disadvantages of time restricted eating
When you first try time restricted eating, chances are you will feel a bit hungry at the moments you would normally eat. However, soon you will feel completely fine, and even great, skipping a meal.
Some people might start overeating due to increased hunger after time restricted eating. For these people this might not be the best routine.
While time restricted feeding is great for your health, some benefits are not as great as an extended fast.
There is a proces in your body called “autophagy”. Autophagy is your body recycling damaged cells from your body. Time restricted feeding does cause some autophagy but in general the amount of autophagy happening is greatest after 72 hours of fasting.
Time restricted feeding is something great to add to your daily routine. The advantages far outweigh the disadvantages.
Semi-extended fasts
Semi-extended fasts last up to 48-72 hours. The difference with fasts longer than that is that semi-extended fasts are still fairly easy to implement in your life.
If you eat a good diet your stores of micronutrients won’t run out that fast, even if you don’t eat anything. The only minerals you might want to consume during your fast are electrolytes like sodium, magnesium and potassium.
Certainly if you live in a hot climate or plan to exercise you should plan these micronutrients in during your fast.
As said semi-extended fasts provide even greater health benefits and more body fat burning than time-restricted eating.
Extended fasts
Extended fasts is the term used for fasts longer than 72 hours. The advantages over semi-extended fasts are more calorie burning and more fasting advantages.
The downside of extended fasts is that they need to be planned more carefully. Chances are that you will run out of micronutrients during this time. That means you will have to strategically add them to your fasting diet or you can get in trouble.
Extended fasts are usually done under medical supervision due to their complexity. It’s important that you inform yourself well before even thinking about doing them.
Potential side effects of fasting
While not eating can certainly offer many benefits for losing weight, there are also some potential side effects. Sometimes doing a few small things can help you avoid these side effects.
- Hunger
- Weak
- Tired
- Dizzy
- Headache
Potential headaches are often because of low salt and water intake. This is easy to solve by adding some salt to a glass of water and drinking it. You can also supplement with other electrolytes like magnesium and potassium.
It’s possible that your body is not used to converting fat into usable energy. This can lead to you feeling tired, hungry, and weak. Over time these things should go away. One way to avoid this is by eating a lower-carb diet leading up to your time period of not eating.
Micronutrient deficiencies
This is a potential downside of not eating extended periods of time. You have to consume more food in a shorter amount of time to reach your daily requirements. Vitamins and minerals are important for both short and long term health and weight loss.
With lower durations like time-restricted eating, this shouldn’t be too much of a problem. On the other hand, doing multiple 24 hour periods of not eating a week could cause this if you don’t pay enough attention to your diet.
Potential for disordered eating
While it can definitely offer benefits, fasting can also become an unhealthy habit if done incorrectly and with the wrong mindset.
Besides the potential physical health consequences of disordered eating, it can also be a reason for unhealthy emotions about food. This in turn can lead to more negative physical health side effects.
If you notice you are developing some kind of disordered eating due to fasting you likely want to postpone doing it for now. Talking about this with friends, family, and mental health professionals may help you avoid disordered eating.
Refeeding syndrome
Refeeding syndrome is a metabolic disturbance that can follow after extended times of fasting. The risk on refeeding syndrome rises the longer you fast. If you are a healthy adult fasts up to 24 hours are generally not enough to put you at risk for refeeding syndrome (1).
Preventing refeeding syndrome involves strategically re-implementing nutrients. Since this is a delicate process you generally want to do extended fasts in a clinical setting.
What’s next
Once you have decided which kinds of fasting you want to do you can start planning a fast to lose weight.
You can’t always predict exactly how you will react to which kinds of fasts. But you will never figure it out if you never try one.
Make sure to consult with your doctor before doing one and listen to your body.
Fasting is an extremely healthy thing to do if done right so it is almost certainly worth it to figure out how you can implement it in your life.
