Intermittent and Prolonged Fasting: What You Should Watch Out For

Intermittent and prolonged fasting have shown some major breakthroughs when it comes to health improvement, weight loss, and overall well-being.

However, as with any other health practice, particularly one as severe and strict as fasting, some side effects are inevitable. Maybe you are already a fasting practitioner, or you are just looking to get started? Nevertheless it is crucial to understand how fasting can affect one’s body and mind in a negative way, so you can prevent it from happening with the right actions.

Fasting has a good and a bad side, but for most people who have succeeded with it and found results, the bad side can be managed and surpassed.

Here are some common side effects of fasting and how to fix them:

1. Hunger

Humans have been eating several meals a day for hundreds of years. We can’t just switch to a caveman eating pattern and expect everything to be normal. Hunger must occur, at least in the beginning stages of fasting. The first week is when the hunger peaks, and as the days go by your body will adapt and the sensation of hunger is going to diminish. Try black coffee or tea with no sugar to suppress hungry.

Drinking tons of water can help, since it keeps your belly full and aids with satiety. Within 30 minutes of waking up, aim to drink around 12 ounces of water with a dash of lemon. This nifty trick can prevent hunger, and it won’t break your fast (1).

2. Cravings

During a fasting period, you are going through extra-long periods without eating. Chances are, you’ll most likely think about it. That’s when cravings kick in.

All the comfort foods, sweet, snacks, fizzy-drinks, and refined carbohydrates will draw you towards them. This is not a coincidence, since the body is looking for a quick glucose hit, its primary energy source. Willpower is important here.

Do whatever it takes, just don’t eat food. Fighting these cravings will make your body burn fat as fuel. Just remember that.

3. Lower Energy/Reduced Athletic Performance

The fasting switch will definitely impact your energy. As the body uses fat storage as its primary source of energy, expect to feel a bit sluggish and unmotivated for a couple of weeks.

As far as athletic performance goes, obviously you’ll take a hit here as well. Research has shown that athletic output is usually impaired when fasting.

In a 2005 study, researchers tested athletic performance of runners during Ramadhan and during the non-fasting time. They found that athletic performance of the athletes reduced significantly during the fasting period. Other studies, show very similar results.

So it may be best to shorten workout sessions. Try to still give your best, but don’t exceed your limits (2).

4. Headaches

Another common side effect of fasting are headaches. One of the reasons headaches occur would be the lack of quick energy found in simple carbs. However, dehydration can also be a factor which induces headaches. An improper intake of water during fasting can affect electrolyte imbalances which further lead to headaches and migraines.

In order to avoid this, feel free to drink electrolyte water or zero-calorie electrolyte drinks. Plenty of regular water can also do the trick (3).

You may consider researching and adding electrolytes into you fasting strategy. Calcium, Magnesium, Potassium, Sodium, Zinc will all affect electrolytes, muscle contractions and nerve signaling. Check out more on electrolytes and the pro’s and con’s on google.

5. Heartburn

A painful burning feeling in your chest or throat is something you may experience during fasting as well. Our stomach produces acid that digests the food we eat, and fasting could disrupt this process. The outcome could be just mild discomfort, although some people reported bigger issues.

With time, this side effect should go away. Use ginger tea during your fasting period, it has great soothing and anti-inflammatory benefits. Again, don’t forget to drink plenty of water.

6. Constipation

Sudden changes in your eating regime, especially if combined with various diets, can lead to constipation and stomach distress.

There are a few things you should do to avoid this problem:

- Not enough fiber. Incorporate more soluble and insoluble fiber in your diet.

- Electrolyte imbalance. Add electrolyte water or no-calorie electrolyte drinks. Don’t forget to drink plain water as well.

- Add probiotics and fermented foods to your diet.

If the issue of constipation and stomach aches persists, consult your doctor (4).

7. Feeling Cold

The sensation of cold hands and feet while fasting is fairly common. There is a good reason for this. During a fasting period, blood flow is centered on the body’s fat stores. Adipose tissue blood flow helps move fat from trouble areas to your muscles, where it can be burned as fuel.

While it is a good thing, the cold feeling can be quite uncomfortable. Combat coldness with hot beverages such as tea and coffee, take warm showers, and wear extra layers of clothing.

8. Mood Swings

It is not unusual to experience frequent mood swings when practicing any form of fasting. And while some feel a boost of energy and motivation when starting out, others encounter signs of depression and unhappiness. The sense of obligation that one carries during a fasting period can be a burden some people won’t stand.

If you’re feeling down for a longer period of time, it might be best to stop fasting and get in touch with a registered dietitian, or psychologist. They will create a proper fasting schedule according to the needs of your body and mind.

9. Decreased Calorie Intake

“If you decrease your weekly and/or monthly calorie intake you have to lose weight eventually” right. Think about if you have 650kcal per meal each day for a month that is (2000 kcal. per day x 30days = 60,000kcal per month.). Now imagine that you cut out 3 meals per week - 3 x 650 kcal. = 2000 kcal. per week x 4 weeks, which comes out to 8000 kcal. less per month or 52,000 kcal. Over a year (60,000kcal/month x 12 = 720,000kcal/yr vs 52,000kcal/month x 12 = 600,000kcal.) which is a difference of 120,000 kcal. or 34lbs per year. But breaking your fast is crucial and you still have to eat healthy for optimal health and cellular function. Obviously, it is more scientifically complicated than that. Hormones, metabolism, genetics, exercise, sleep, stress, and timing of eating all come into play for weight management.

10. Tips

Intermittent Fast every other day to allow your body to adjust and also not to go into starvation mode. People fast too much and you need to let your body get fat adapted so start out every other for success.

Try doing a 24-48fast once a month to reset your digestive system, nervous system, and hormonal system. This will work as a detox and reset your body. Get benefits of longer fasts such as stem cell regeneration, killing cancer cells, increase HGH human growth hormone (aka building muscle) and improving mitochondria for more energy and better immunity.

Breaking your fast with low sugar and healthy choices is very important. Most people go on a binge session after a fast, like eating a pizza. This is high in calories, high in sugar/glycemic index, dairy, lots of fat. They end up ruining the benefits of the fasting reset and don’t see the scale change. Try having a protein shake with apple cider vinegar, almond milk, and some MCT oil. Then 1-2hrs later have a full meal. This will wake up the digestion and nervous system to get you back in working order.


Fasting is definitely an interesting eating pattern. We have the ability to go long periods of time without food, however that doesn’t mean you should do so. As far as evidence go, fasting has proven to provide various benefits, ranging from weight loss to better overall health. But, we also presented some negative sides of fasting in this article.

Therefore, the choice is yours. Give any form of fasting a try, evaluate the effects and ultimately decide if it suits you.

It’s not the end of the world if fasting doesn’t work for you. You can still lose weight and be healthy eating several meals a day.






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