The Negative Aspects of Intermittent Fasting

author avatar Dr. Eric Berg 08/31/2023

You know there are many potential benefits from intermittent fasting, right?

They include:

  • Significant weight loss
  • Improved mental clarity
  • More energy
  • Hormone re-balancing
  • Repair of your metabolism

All this without counting calories or risking side effects like extreme hunger and irritability, dizziness from blood sugar crashes, or ruining your metabolism. Plus more, which I’ll get to in a minute.

Obviously I’m a huge fan of intermittent fasting. I’ve seen firsthand the dramatic improvements people have experienced. In many cases, they’ve completely turned around their health and well-being along with losing serious amounts of body fat.

And fasting is simple: it's a period of alternating eating periods; say, within an 8 hour window each day, with not eating for the rest of the 24 hours.

These benefits are available to you, too.

But in the interest of transparency, I want you to know that there are some cons to fasting to be aware of in case any of them apply to you.


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The 5 Downsides Of Intermittent Fasting

Let’s take a look at what they are.

#1 You’re going to lose so much weight, you’ll need to buy new clothes. This is expensive! You might go broke buying new clothes. Although this sounds a little bit tongue-in-cheek, I’m serious. Plan for a new wardrobe, or at least to get your favorite items tailored for your new, smaller size.

a young woman wearing jeans that are way too big

Before you go out, make sure you try on something you haven’t worn for a while to see if it still fits. It might be way too big, and leave you scrambling for clothes that fit you better.

#2 Fasting isn’t good for people who are trying to gain weight. If you’re thin, and want to gain weight, fasting isn’t for you. I realize you may still struggle with issues like Fat Storing Hormone resistance or being what’s called skinny fat - where you have normal body mass index but still have a high amount of fat as well as significant inflammation that puts you at risk for cardiovascular disease.

How do you know you might be skinny fat? Well, for example, you have a muffin top. You can’t even do one pushup because you’re so out of shape. Or, your diet is unhealthy. Going on the Healthy KetoTM diet will help address your skinny fat issues.

#3 Inhibits your social life with family and friends. When they want to go out and gorge on unhealthy food and drinks, you’ve got to stay home and stick to your fasting plan. Or, you could go and hang out with them but not eat, and stick to fasting-approved drinks like coffee, tea, or sparkling (or plain) water.

You don’t want to become a hermit while you’re fasting. That would be no fun at all; not to mention, it would make it challenging to stick to your commitment. Don’t deprive yourself of the company of people you enjoy, just make sure you’re setting yourself up for fasting success.

a man saying no to various kinds of junk food

#4 May offend people. A lot of people want to offer you food, and may feel offended if you decline what they’re offering. Interestingly, this one is more common than you might think.

They may feel offended because it seems like you rejected their food. Perhaps they feel awkward eating and drinking in front of you, so they try to make it your fault.

You don’t need to launch into long explanations about why you’re fasting. Sometimes it’s easiest to simply say, “I’m sensitive to (or allergic to) that, and can’t eat it,”

Or if you think someone might feel awkward eating in front of you, let them know in advance that it’s perfectly fine to eat alongside you while you’re fasting.

#5 You might miss the sensation of food. If you have a long-time habit of crunching on chips at night, you’re going to miss that sensation. If you’re fasting, you can’t do that anymore!

This is one where you will need to remind yourself of your commitment, and the results you want to achieve, because there really is no fasting substitute for crunching late at night. However, if during your eating window you want to crunch, try putting a healthy fat such as almond butter on some celery sticks. You can crunch a few of those to satisfy your food sensation.

#6 Not good for someone with an eating disorder. If you already have an unhealthy relationship with food, don’t fast. Especially if you struggle with anorexia nervosa, fasting isn’t right for you because you already over-restrict your food.

Having said that, the combination of keto and intermittent fasting can be extremely helpful to treat an eating disorder if done correctly, and if you are particularly focused on eating a healthy diet to correct mood disorders and blood sugar swings that come from an unhealthy, high-carbohydrate diet.

Bottom line, though: fasting on its own, and not done correctly in tandem with keto, isn’t for you.

You can tell that there are some downsides to fasting. But before you get bummed out, let’s take a look at the pros and cons side by side.


What Happens When You Compare The Pros And Cons?

Unless you’re one of the comparatively few people who are skinny-fat, or have an eating disorder, I suggest you weigh (get it?!) these cons against the pros. Remember I mentioned I’d cover more of the health benefits?

Here’s what is possible for you when you fast and eat a healthy diet, preferably keto. You can:

  • Lose your belly
  • Regrow your brain cells (called neurogenesis), which helps decrease Alzheimer’s symptoms, improve your memory, and regain cognitive function
  • Fix Fat Storing Hormone resistance so your body regains its Fat Storing Hormone sensitivity
  • Eliminate symptoms of blood sugar fluctuations
  • Decrease your risk of heart problems, as well as of cancer and stroke
  • Lower high blood pressure to a healthy level


a woman measuring the loss of her belly fat

When you balance the pros and cons, the choice looks pretty easy, doesn’t it?


The Takeaway: Intermittent Fasting Is Probably Right For You

I certainly don’t mean to scare you by telling you the potential downsides to intermittent fasting. It’s probably right for you, unless you fall into one of the fairly small categories of skinny-fat or have an eating disorder.

The other cons are very straightforward to remedy. Yes, you may be temporarily uncomfortable when, for instance, you decline food and the person offering is offended. But your discomfort will be more than outweighed by the substantial health improvements that await you.

So when you feel awkward, remind yourself of your goals. If you’ve been fasting and have already experienced some improvements, remind yourself of those too.

You made a commitment to yourself to achieve better health along with a better life - because without good health, your life will suffer.

I know you can do this, because I’ve seen many people stick with it and have wonderful success.

You can too.

So, go ahead. Make the commitment to yourself now.

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Disclaimer: Our educational content is not meant or intended for medical advice or treatment.

Editor’s Note: This post has been updated for quality and relevancy.

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