The Benefits of Intermittent Fasting Might Be Positive, But What Are the Side Effects?

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While intermittent fasting might feel like a buzzword in the world of wellness, it’s a style of eating that is extremely popular. And, for many people, intermittent fasting has a number of positive benefits including lower blood pressure, improved blood sugar control and decreased risk factors of heart disease.

Others can also experience weight loss and reduced oxidative stress and inflammation within the body as a result of this eating pattern. While these benefits are indeed positive, intermittent fasting does come with its own set of side effects, despite being considered to be safe for most people, says Healthline. Here are a few of the most common side effects:


One of the less surprising side effects of intermittent fasting is hunger. This style of eating involves periods of fasting (with the most common form being 16:8 — 16 hours fasting with an eating period of eight hours) so if you’re not having your first meal until midday, chances are you might get a little hungry.

Choosing to eat within certain periods can also restrict the number of calories you consume in a single day, which can also lead to hunger. But, according to research, it seems that hunger is most common when starting this eating method and usually only last a few days as your body adapts to fasting.

Bad Breath

Bad breath is an unfortunate but extremely common side effect of intermittent fasting. While not all people who practice intermittent fasting experience bad breath, those who do probably experience what is often described as a fruity or metallic taste in their mouth.

If this is happening to you, don’t fret on it too much as it’s completely normal. “When fasting or eating a ‘ketogenic diet’, your body can enter a state of ketosis. This process of breaking down fat for energy releases ketone bodies which are a gaseous compound that produce an odour,” dentist Dr Lewis Ehrlich from Sydney Holistic Dentist Centre, told POPSUGAR Australia.


Headaches and lightheadedness are pretty common when intermittent fasting. In fact, according to Healthline, researchers have found that “fasting headaches”, as they are known, are usually located in the frontal region of the brain and the pain is usually mild to moderate in intensity.

Research has also pinpointed that people who commonly experience headaches are more likely to get them during fasting than those are aren’t so headache-prone. As for why this happens, researchers seems to think that low blood sugar and caffeine withdrawal may contribute to these fasting headaches.

Digestive Issues

Intermittent fasting can also cause digestive problems in some people, including constipation, bloating and at times, nausea. Reducing your food intake can negatively effect digestion, and trigger things constipation. According to Healthline, changes in diet commonly associated with intermittent fasting can also cause bloating and diarrhea in some people.

To avoid constipation from occurring, make sure to fill your plate with fibre-rich foods like avocadoes, berries, kale, spinach and lentils. It’s also important to make sure you’re consuming enough water while fasting, as dehydration can worsen constipation.

Low Energy

While some people who practice intermittent fasting don’t experience a change to their energy levels, some definitely notice the difference. Fatigue and low energy levels are a pretty common side effect of fasting, leaving you feeling tired. If this is something you experience, try making your periods of eating a little bigger so you can consume food earlier in the day, which should help with your energy levels.

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