6 Funky Side Effects of Intermittent Fasting.


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When I first started intermittent fasting for weight loss, I experienced some pretty funky side effects. Side effects I never experienced from other weight loss plans before. From dry mouth to wild dreams, it seemed like my body was living in some strange alternate dimension! 

As it turns out, when the body changes its core method of processing food and fat, the body lets you know that these changes are taking place by acting a little funky during that adaptation process.

The good news is that these intermittent fasting side effects don’t happen to everyone, and, even better, if they do, they don’t last forever!

Let’s take a look at these 6 funky side effects of intermittent fasting, that I personally experienced, and what I did to get over those funky humps!

Dry Mouth/Keto Breath.

Feeling a little funky in the mouth? 

Dry mouth (or Keto breath) is a very common side effect of IF. I didn’t experience mouth funk at first with my 16/8 fasting schedule, but once I went to an 18/6 fasting schedule, there was nary a drop of fluid in my mouth for weeks. 

What causes this strange side effect? 

Dry mouth/Keto breath is typically caused when the body enters the state of ketosis and starts burning fat for fuel. 

Ketosis (as defined by WebMd) is a process that happens when your body doesn’t have enough carbohydrates to burn for energy. Instead, it burns fat and makes things called ketones, which it can use for fuel.

Ketosis & Intermittent Fasting – It is said that fasting for 12+ hours can effectively put your body into a state of ketosis even if you are not living a ketogenic lifestyle. However, that timing will most likely differ from person to person. Some intermittent fasters will reach ketosis after that 12 hour period, while it may take other intermittent fasters several days to burn through their glycogen stores before reaching the ketogenic state.

Dry mouth/Keto Breath is a good indicator that you are in ketosis and that your body is burning stored fat for fuel.

But, this does not happen to everyone so it is very possible that you are in ketosis even if you don’t have funky breath!

Will it last forever? 

No! Once your body starts to adapt to IF, your bad breath will subside and your dry mouth will start to go away. 

I experienced dry mouth for about 2-3 weeks after I switched from a 16/8 intermittent fasting schedule to an 18/6 intermittent fasting schedule.

It was pretty intense, it was like the Sahara Desert in my mouth, but it did not last.

My kids complained, my husband didn’t kiss me and I did EVERYTHING I could do to NOT to talk too close to people at work, but it was all good. I found a solution that helped me during that time (see below). And, like I said, it didn’t last.

How to manage the yuck?

Most people will tell you to drink a lot of water, but I didn’t find this particularly helpful in managing my dry mouth. While I do drink plenty of water to keep my body hydrated, I found no difference in dry mouth with the added H2O. 

In the end, I bought WOW drops. They are really powerful mouth drops made from peppermint oil. You put a drop (or less) on your tongue and WOW! It’s like a peppermint explosion in your mouth. They are really great for clearing the sinuses, too!

WOW drops and water aside, I didn’t find anything other than “time” to really solve this problem. However, the WOW drops allowed me to, at least, talk to people without my breath knocking them out.

NOTE: If you are fasting CLEAN, you will want to be careful with the products you choose. If you are in a fasted state, you could break your fast with gum, lozenges, mouthwash, herbal teas, etc. The WOW drops will not break your fast.


No more morning poops? Give it some time, like many funky IF side effects, your constipation will start to go away once your body adapts.

I did suffer from constipation when I switched my intermittent fasting schedule to 18/6. My poos averaged about every 2-3 days.

For someone who relies on her morning poos, I was a little concerned. I don’t like poo babies in my belly, but to my surprise, I wasn’t bloated or gassy, so I wasn’t too concerned. 

Side Note: My guess about the lack of bloating and gas has a lot to do with my fasting schedule.

During the time when I was constipated, I would close my eating window at 7:00pm and open it at 1:00pm the following. My best guess is that by doing this I allowed my body time to manage and digest the food I had consumed prior to going to bed and after I woke up. This reduced any bloat or gas I had when I was constipated.

It’s a theory and it seems to make sense for me. In any case, I’m happy to report that I’m back to my “regular” regular self again and have been for a good long while.

What you can do to get things moving again?

Drink more water. I mean, water seems to be the antidote for most of our ailments, right?

Also, take a look at your food intake. Are you eating enough fiber? Too many processed foods? Try swapping some of your processed foods with whole foods. 

I’m not a huge fiber fan because it just doesn’t sit well with my stomach, but when I focus on getting whole unprocessed foods, I have no issues with my daily movement.

Side Note: For those of you just starting out, eating ALL THE THINGS is common when you first start IFing. If that’s you, ALL THOSE THINGS may be causing a back-up. You may need to take a step back to determine if ALL THE THINGS is really necessary and what THINGS you can remove from your eating window to help get your flow moving again.

If you are experiencing pain or severe constipation, consult your doctor!

Wild Dreams.

I have no idea why this happens, but many IFers experience wild, vivid dreams. There is some speculation as to why this may happen, but no real conclusive evidence. 

I have experienced (and still experience) this first hand and it can be pretty crazy. 

Sweet dreams!

Sign up: I talk about what to eat while intermittent fasting in my FREE 3 Day Short Course.


For me, I had a very difficult time sleeping in the early stages of IF because I was going to bed HUNGRY. 

Prior to IF, I was a nighttime snacker. I would have a little (or big) snack every night very close to my bedtime. When I removed that snack, creating a few hours before my last meal and bedtime, my belly was growling.

That, too, went away with time. 

It’s also said that intermittent fasting clears the brain, so much so, that it can make the brain more active, thus making it harder to fall asleep.

What to do?

I talk about this a lot more in my Free 3 day IF Short Course, but create routine. 

Let your body and your brain know what to expect. Once your body has adapted to intermittent fasting it will become easier for you to fall asleep. 

Lately, I’ve been participating in my beautiful friend Amber’s Daily Virtual Guided Relaxation. During the quarantine months, she’s been hosting a 10-15 minute guided relaxation every morning and evening via zoom. It is so lovely and really calms the body and the mind.

Alternate Option #1: Another option might be to try melatonin. There are members in my FB Group that swear by just a little melatonin each night to get them some ZZZs.

Alternate Option #2: CBD oil. I have a friend who swears by CBD oil to help get her to sleep. Now, I don’t know much about CBD oil, it’s potency or the like, but it’s out there and it’s an option. If you are interested in using CBD oil, do your homework to see what might be a good option for you.

Read: 2 Tips to Create Structure in Your Day.


Like many, I experienced headaches when I started intermittent fasting. It didn’t happen on my 16/8 fasting schedule, but it did hit me pretty hard when I switched to an 18/6 intermittent fasting schedule. 

Headaches can occur for multiple reasons, but for us IFer’s it’s most likely because of a drop in blood sugar or dehydration. 

For me, I know it was because of a drop in blood sugar. I was going longer without food when I was on the 18/6 plan, so that diagnosis just makes sense. 

What to do to combat the headaches?

For me, I had to take a look at WHAT I was eating in my eating window.

Fortunately, with a few adjustments to what I ate during my feast (added some more high-fat foods) and “time”, my body started to better adapt to the 18/6 plan and the headaches went away.

What else can you do to combat the headaches?

Welp, guess what, water is the antidote once again! 

Stay hydrated. 

Many people will put a few drops of Himalayan sea salt under their tounges to accompany their water intake to help battle dehydration. 

Personally, I like to make my own sparkling mineral water with my Soda Stream and add a few Trace Mineral Drops.

What Worked for Me: I have been suffering from migraines since I’ve been about 8 years old. They can be awful. If I start to experience a headache I take ibuprofen. While I did up my water intake when I experienced headaches while intermittent fasting, I also decided to add pain killers to the protocol to help me manage those occasions when the headaches hit.

I am very happy to report that I only experienced 1-2 headaches after making my switch to a 18/6 intermittent fasting plan. I haven’t experienced an intermittent fasting induced headache for a very long while.

Important Note: Here’s the deal. Hopefully, you know your body well enough to know when something’s not right. If you’re experiencing significant headaches with IF, talk to your doctor. 

While there is an adaptation phase, and while all of that should eventually go away, you don’t want to push yourself to “harm” in an attempt to lose your weight. 

Take a step back, figure it out, and then move forward in whatever direction works best for you.

Hair Loss.

This happens! This is usually due to a lack of nutrients like protein and B vitamins. Many IFers see hair loss at the beginning of their journeys, but report that their hair started to grow back over time. 

If you notice you are losing your hair, take a look at what you are eating during your window. Having a shorter eating window limits the amount of nutrient-rich foods that we can consume, so make sure what you are eating during your window is full of the good stuff!

Side note: I started to add Collagen Peptides to my feasting window again. While my hair isn’t falling out, I am getting older and my ponytail is starting to look a little sad. I’m hoping the collagen will help with my hair, nails, and skin as I age.

What about you?

Our bodies have most likely lived their lives burning fuel from the food we ingest throughout our day. When we switch the mechanics of what we do on a daily basis in terms of food consumption and meal times, allowing our bodies to start burning our stored fuel from our stored fat, adjustments need to be made.

These adjustments result in the funky side effects we can experience when we start intermittent fasting.

Have you experienced any of these funky side effects of intermittent fasting? If so, add them to the comment AND let me know if there is anything that you did to combat those funky side effects!

Check out the Toolkit!

Take a minute and check out my Intermittent Fasting Toolkit! From the books I read to the products I use, everything in this very simple toolkit helps keep me on track with my intermittent fasting lifestyle.

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Disclaimer: The information in this email is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on the stuckassdown blog.


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