Intermittent Fasting Side Effects

One of the most effective (and quickest) ways to lose weight is by restricting yourself to a 500 calorie diet. And, as well as reducing your weight, there are many health benefits of fasting which make it an attractive way to improve your life. In particular the effects of intermittent fasting on metabolism combined with a reduction in high blood pressure are benefits which cannot be ignored.

However, as with all changes to your diet, there are a number of side effects that result from intermittent fasting. Naturally, undertaking a 500 calorie diet is going to call for some extreme measures, so it’s crucial that you fully understand the side effects in order to make a decision on whether fasting is right for you.

Intermittent Fasting Side Effects

Done correctly, intermittent fasting should help you achieve that weight loss you’ve always wanted and doesn’t necessarily have to feel like a nightmarish marathon of deprivation. Not everyone is fully aware of the side effects from fasting, though, and the onset of these side effects can be very discouraging for your motivation.

The 3 Week Diet

And some of these effects aren’t even immediately visible, so they can come as a real surprise when they do appear. To help you understand the negative effects of fasting are, we’re going to take a look at the most common side effects you’re likely to experience and how you can help minimize their impact on your daily life.

Intermittent fasting side effects include:

  • Tiredness – Food provides the body with energy, so it’s no surprise to discover that one of the major side effects of intermittent fasting is the onset of fatigue. And this is particularly unpleasant as the lack of energy means that you can really struggle to get through the day. The end result is that your body then begins to crave high calorie foods and you’ll find yourself tempted to indulge. In order to avoid this side effect, planning and spacing your meals out correctly is crucial to prevent any major dips in energy.
  • Mood – Completing a bout of intermittent fasting can be a stressful affair and not just because of the reduction in calories. Planning and sticking to a low calorie diet can cause participants to become stressed and suffer severe mood swings. An obsession with food is often reported, so the conflict between eating what the diet dictates and what your mind wants can cause frustration levels to skyrocket. The best way to navigate this is by tinkering with your diet until you find a variation which provides the least stress.
  • Concentration – It’s not just physical fatigue that can set in when you’re in the midst of a very low calorie diet (VLCD), you also have to combat the mental fatigue which can seriously disrupt your concentration levels. Dieters often report that a mental fog descends upon them and leaves them unable to concentrate on their day to day activities – this can cause real ramifications for your performance at work and your ability to operate machinery (particularly if you drive). In order to prevent your focus drifting too much, try drinking coffee to keep on track. (Remember to check coffee pros and cons as well).

The 3 Week Diet


  • Impairs sporting performance – Intermittent fasting can put a real strain on your sporting performance and the more intense an exercise, the more it is affected by a VLCD. Therefore, if you partake in particularly strenuous exercises such as powerlifting and high intensity interval training (HIIT) you’re going to notice a real drop in your performance when fasting. This is due to the energy deficit incurred by taking in significantly fewer calories, so it’s recommended that exercise only takes place on days where you’re not fasting.
  • Affect Women’s Hormones – Many women undertake low calorie diets, but one of the most dramatic side effects won’t become apparent until you’re well in to your diet. Due to decreased energy intake, women’s hormones can begin behaving erratically which confuses the body’s normal operation; this can result in metabolic changes and throw menstrual cycles completely off schedule or even shut them down altogether. If you find that this starts to affect you then switching to an 800 calorie diet for your fast days should improve the situation.
  • Severe hunger pains – With the limited number of calories you’re restricting yourself to it’s no surprise that one of the most common side effects is hunger pains. In some cases, these hunger pains are severe enough to disrupt your sleep. And, in turn, these sorts of effects can soon lead to irritability and, eventually, a determination quit the fast and binge on food immediately. However, you can counter these hunger pains by supplementing with liquids to keep you full e.g. a cup of green tea before bed instead of a late night snack packed full of calories which will take you over your 500 calorie limit.

Final Thoughts:

As you can see, there are several side effects to intermittent fasting and it’s fair to say that they’re not effects that you can just ignore. They’re all capable of causing real disruption to your daily lives and even create an environment that your body is unable to function in correctly. And nobody wants to put themselves through this, but neither does anybody want to fail at intermittent fasting. Therefore, it’s important that you find a level of balance between your diet and the side effects to help encourage yourself to continue.

It’s impossible to fast and experience no side effects at all, but if you’re able to put a plan into place then you can reduce the impact of these side effects. Whilst you will certainly have to tinker with this plan as your fasting progresses, it’s essential that you have one in place before you start your fast. Good planning will ensure that you’re able to focus on your fasting with the minimum disruption and this will make a real difference to your weight loss goals. It won’t always be easy, but just remember how much of an achievement it will be if you can overcome these obstacles.

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