Why Am I GAINING Weight With INTERMITTENT FASTING: 4 Intermittent Fasting Mistakes That Can Lead To Weight Gain

Intermittent Fasting can be a great way to lose weight as part of a healthy lifestyle. However, there are some potential Intermittent Fasting mistakes that can lead to unwanted weight gain.  This guide will tell you what you may be doing wrong and give you tips on how to succeed!

4 Intermittent Fasting Mistakes That Can Lead To Weight Gain

If you’ve been following me for a while, you’ll know that I follow an Intermittent Fasting (also called IF) lifestyle. It has been a key component of why I feel so amazing and healthy at this point in my life.

Remember, it wasn’t always that way. I definitely struggled with my weight for many years (see my story here) and didn’t feel good about myself at all. I had some yo-yo dieting going on and a love for junk food, and seriously, the two did not mix.

But now that I am on the right track (thanks to Intermittent Fasting and exercise—a great combo), it’s so much easier to be healthy. One thing I think is great about IF is that it suits every type of diet you prefer, from keto to vegan to paleo, and so on.

So yes, I used IF for weight loss, and chances are you are reading this post because you are, too. 

If you are wondering “why am I gaining weight with Intermittent Fasting?”, don’t stress. You are not alone. I get asked a lot how weight gain factors in when you are trying so hard to eat healthily.

We’re going to look at that now and let you know where things may be going wrong. I’ll also give you the info you need to succeed.

Losing weight with Intermittent Fasting is entirely possible and trust me, we’ll get you there!

Side view of summer corn edamame salad, filled with cooked quinoa, sliced red onions, edamame, and fresh corn.


Intermittent Fasting is basically an eating pattern. It’s pretty simple really, as you have periods when you eat (eating window) and periods when you don’t eat (fasting window).

I don’t call it a diet, even though this regimen can help you to lose unwanted pounds. It’s more of a lifestyle change to be honest, and a change that pays off when you make it a regular thing.

Choose an IF plan that fits in with your day and your habits. That’s the best way to make it work for you. 

Close up view from the top of Chipotle Black Beans Stuffed Baked Potato which is garnished with avocado and black beans.


I go into more detail in my post Does Intermittent Fasting Work for Weight Loss: A Beginner’s Guide to Intermittent Fasting, but here is a brief rundown:


A lot depends on your body and how it reacts to the fasting. Some people can lose 10 pounds in a month, whereas others will lose an average of a pound or two a week.

Several studies have proven that IF helps you lose weight. One, in particular, concluded that IF participants lost between 4.6% and 13.0% of their baseline body weight over 8 weeks to 1 year.  For sure, those who exercised (see my post on the best time to exercise here) saw increased results over those who did not. Daily activity is good for you in many ways, so get out there and move!

Overhead image of a blue skillet containing Healthy Beef With Broccoli ready to serve, with a wooden spoon in the skillet also.



Paying attention to what you eat is just as important, or even more so, than when you eat. You see, if you eat a lot of carbs and high-calorie foods full of sugar, you will, no doubt, gain weight as opposed to losing it. You’ve got to eat what your body needs in calories, not overeat just because you know you won’t be eating for another 16 hours (if you follow the 16:8 plan as I do).

Instead, eat clean. If you do that, you’ll have no issues. Fresh fruits, veggies, lean meats, fish, and whole grains are foods to eat. Sounds great, right? Calculate your macros (I explain how to do it here) and eat healthily to lose weight.

Keep an eye on the calories, too. If you are eating from the time your window opens until just before the fasting window, chances are, you are consuming too much. To lose weight you do want to reduce calories—but it’s a fine balance and needs to be a nutritional one.


This may come as a surprise, but not eating enough can cause issues. How is that? If you don’t eat enough in your eating window, you increase the chances of binge eating in your next window due to sheer starvation. You’ll be so hungry, you may start eating and not stop.

As well, the body stores food to protect itself. Your body will sense the need to stock up on reserves and may store those extra pounds as fat instead of lean muscle. So again, calculate your macros to see the number of calories your body needs (it’s not that complicated to figure out your macros, trust me) and you’ll still nourish your body while losing weight.

If you are struggling with not eating during the fasting period and then bingeing during your eating window, try reducing the fasting period from 16 hours to 14 or even 12. Once you get things under control, you can gradually expand the fasting period until you are back at 16 hours. If you are trying the 24-hour fast, make it a 20-hour fast to gain control over how you are eating. The same principal can be applied to any of the fasting regimens. The main thing is to eat healthily when you do eat, and to eat enough to nourish the body.

Overhead image of a hand with spoon scooping out some of the slow cooker chicken cauliflower curry from the ceramic bowl.


I’ve been writing a few posts lately about protein and I cannot stress enough how important it is for the body! Whether it’s vegan proteinprotein powders, or sources like lean meat and chicken, protein is an essential building block. Protein is important for muscle mass and recovery after you exercise. It’s good for bone health, too.

Protein fills you up as well, helping you make it from the fasting window to the eating window. If you are consuming foods that are sugary and processed, your insulin levels spike, signaling your body to store fat. At the same time, this spike blocks leptin, the hormone that tells you that you are full.

So rather than filling up on carbs and refined sugar, go for delicious lean protein!


eat clean MOST of the time (on holidays and special occasions or dinners out, of course, I eat what appeals to me) and I’d advise that you do, too, especially if you are asking “why am I gaining weight with intermittent fasting”.

There are reasons to eat clean when following an Intermittent Fasting regimen:

Remember, clean eating is not restrictive. You can still have tons of amazing foods—and even dessert!

Overhead image of a mason jar containing chocolate banana protein smoothie, with a striped straw sticking out of the jar and banana slices around it.


I found that little tips and tricks made a huge impact when I first started out with IF. I’ve compiled a little list of things that helped me:


You can learn a whole lot more about Intermittent Fasting by reading through my other posts. Take a look!

This post contains affiliate links for products I use regularly and highly recommend.

Lacey Baier

Hey there! I’m Lacey Baier and I’d like to welcome you! I’m a healthy lifestyle influencer and the creator of this clean-eating blog and YouTube channel, as well as cleanish, my clean-eating supplement brand. My recipes have been published on Food Network, Good Morning America, FoxNews, Tastemade, Fitness Magazine, and much more. I live in Austin, Texas with my husband and four kiddos. Let’s get started!

19 thoughts on “Why Am I GAINING Weight With INTERMITTENT FASTING: 4 Intermittent Fasting Mistakes That Can Lead To Weight Gain

  1. Hey, I just started 8am-6pm. I only lost 2lbs. It goes up & down. I fast, exercise & use a calorie count. It’s only been about 10 days. I try to drink 30 oz of water daily. Is it too soon to see any results?

  2. If your body is still using sugar/glucose as primary source you will not losse significant weight. Yes you will loose some but when you hit the plateau you have to go one step further and reduce carb intake. I’ve lost 8 kg just by IF in 2 months. The hit a plateau for about 2 weeks. I then switched to a low carb/keto style combined with IF 20/4 and lost an extra 6 kg in aprx 2 weeks. In total went from 85 to 71 kg and feeling awesome. Oh and plus, for exercise i was riding the bike running, long walks… hope this helps

  3. Do you have to count calories. I’m not good at tracking. I am also older and tried 18/6 but I did not lay off the icecream and croissants! So I gained..

    1. Hey Centa! While calorie counting is not generally required for IF, it wouldn’t be a bad idea to bump up focus on calorie intake if you are noticing weight gain. Once you get into a good routine or flow, close watch on calories will no longer be necessary (most likely). I hope this helps! – Jen

  4. None of those apply to me. 1500 calories a day. 20 hour fasting window, water only while fasting. Eating clean. Up 6lbs in a week.

  5. I released 51lbs then 54lbs in 2 years of intermittent fasting. But now 2 and a half years later, I have belly fat again and have started to gain weight! Just 6lbs, But I need to stop. I was recently diagnosed with celiac. So I think it is due to gluten-free products being so highly processed. Or it could be I am eating too little as sometimes I get too busy to eat all day and then have one meal late. Gotta get my groove back because I love how I felt skinnier and just this extra 6lbs looks terrible. Plus, I wanted to go down 10 more!

  6. I started IF about a week ago and I am so hungry with headaches it’s making it hard to continue. Ive been on keto for about 6wks. Any advice is so much appreciated.
    I’m just so hungry

    1. Don’t give up! Start your day with a big glass of water, then your black coffee or tea. Keep drinking that water! Your body is reacting to less food-based hydration. You may even experience some constipation. I’m in week 7 of a 16:8 IF and, trust me, it’s worth it!

  7. Hello everyone. I have always had problems with being overweight. I’ve tried so many methods before. It was better and worse.

  8. I just started intermittent fasting like ten days ago and I noticed my face has started reducing,but I feel my other body are not slimming down ,an scared cos it feels like am really not doing it right,I am on a 20:4 diet,and I only take tea and water,but I eat protein and am not sure if am eating a lot of carbs,please I need to see result,am being body shamed,I take ice cream, sometimes cake during my free window or biscuit,but I reduced the portion,am I on track.

    1. Stick to what you are doing and eat clean. 10 days is too soon to see overall results.It will take time. Give it at least a couple of weeks.

    2. It’s pretty normal Jimmy and keep doing it and you’ll see the result in the next couple weeks. When your fat is burned, the empty place will be replaced with water (it’s just how our cells work) and water is heavier than fat, so you might even see the weight gained in the first 3 weeks. But keep the IF and after your body adapts to the new lifestyle, water will be released and you’ll start seeing the weight loss. Many people said it took them 3-12 weeks to see the result but once you see it, your weight will go down nonstop if you keep eating the right time and the right food.

    3. Hi Jimmy,
      I think the reason is 20:4 IF instead of 16:8 IF. I have been following IF for last 5+ months with 16:8 IF. However, recently I came across a video on YouTube which recommended 20:4 IF for those who are older than 40 years. So I started 20:4 just 5 days back and as a result my body reacted very bad. First, I faced constipation ( I make sure that I take sufficient carbs during me eating window) and today I noticed that instead of weight reduction, I gained 1kg in just 5 days and my fat% also increase at the same level it was 2 months back. Since then I have been visiting websites, blogs to check the reason and in my view 20:4 IF is completely wrong to your body.

    4. Stick to it. I dropped 51lbs in a year and maintained it for another year. It is slow at first then starts to drop off. Up your fiber and water intake, And I drank black coffee with MCT oil and stevia if I got too crazy hungry at night. You can also try a low sodium instant miso soup or veggie broth.

  9. Hey can IF work with Caloric deficit at the same time aswell or it would be to low as you said and would not burn fat?

    1. I was looking up the same thing when I found this forum. The write up mentioned sticking with low-carb foods. If you do this, the body will not be able to store much as fat because the carbs are so low. Think “Keto” but modified. I aim for 35% protein. I get close to my budget some days but because I take in so much protein, I am unable to eat the max amount. Also, my window is smaller than 8 hours so I do not get hungry enough for a 2nd meal before my window ends. To sum up: Focus your meals on protein and healthy fats (olive oil, salmon) and strict on low carbs ( no more than 20-30%). Keep in mind, every body is different so try it and see what happens.

  10. Hi I do intermittent fasting working nights..I stop eating by 6-7pm and don’t eat until my shift is over at 9am. Usually around 10am. What is best to eat when you combine IF with trying to sleep after being up all night and not gain weight? Soup? Cooked veggies? Protein? Need help, please.

    1. As long as you’re following a clean eating diet and eating within your calorie amount, you should be fine, no matter when you’re choosing to eat 🙂

  11. Ive tried this with IF and it has helped out ATON. https://rb.gy/ibqduh
    Tastes a little weird but anything for the weightloss

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