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The Potential Downsides of Intermittent Fasting

We’ve discussed the potential benefits of intermittent fasting, but there are also some possible downsides.

Reduced energy

Because intermittent fasting can involve a prolonged period where you’re not eating, your body may be running on an empty tank for longer than it’s used to.

Studies show that intermittent fasting can cause fatigue, feelings of low energy, irritability, and can make it harder to concentrate — although there’s some evidence that these symptoms may improve with time.

It can be hard to sustain

Many people find it hard to stick to intermittent fasting in the long term, just like many people find it difficult to stick to other diets in the long term.

In one study, 38% of participants in the alternate-day fasting group left the study within the year, compared with 29% of those on the calorie-restricted diet group. However, other studies have found the opposite — people in the intermittent fasting group continued the study longer than those in other diet groups.

If you enjoy eating as a social activity, it’s important to plan your fasting windows or days around occasions like birthday parties, family meals, or dinner with friends.

It’s also important to choose high quality foods when you’re eating and to make sure you drink enough water during fasting periods.

Disordered eating

Although intermittent fasting doesn’t dictate what you can and can’t eat in terms of calories or particular food groups, it can promote disordered eating for those at risk.

Research shows that fasting is linked to both bulimia and binge eating.

Many people will be able to follow intermittent fasting without it negatively impacting their relationship with food, but others could find it triggering.

Who should not try intermittent fasting?

Although intermittent fasting may be safe for some people, those who should avoid it include:

  • Pregnant or breastfeeding women: Although there are no specific studies on intermittent fasting during pregnancy or breastfeeding, women generally need more calories during these periods so should not go on restrictive diets.

  • People with a history of eating disorders: Fasting has been linked to an increased risk of bulimia and binge eating, so it’s not recommended for anyone who has experienced disordered eating in the past.

  • People with type 1 diabetes: People with diabetes or blood sugar problems are at risk of experiencing hypoglycemia with fasting, since the amount of insulin they take needs to be adjusted with fasting.

  • People on medication that needs to be taken with food: If your medication needs to be taken several times a day at mealtimes, cutting out meals could make this impossible.

  • Older adults: Fluctuations in energy intake and glucose concentration can cause falls and fractures in older adults, who may have problems with their balance.

If you have a pre-existing health condition, speak to your doctor before changing your eating patterns.


There are a number of different types of intermittent fasting. With some, you eat within specific time windows. Others involve significantly reducing your calorie intake on certain days of the week.

There is evidence that intermittent fasting can lead to weight loss in the short term. While it may not be any more effective than a traditional calorie-controlled or weight loss diet, it could suit some people better, as it doesn’t limit what you can eat during non-fasting periods.

However, like most diets, intermittent fasting can reduce your energy, could lead to disordered eating, and may be hard to sustain in the long term.

There is evidence that intermittent fasting may help to improve risk factors for type 2 diabetes and heart disease.

We are planning a big, new health event for our practice members for this upcoming February.

We’re calling it FebFast.

After the festivities and, for some of us, the excesses of the Christmas, Holidays and New Year celebrations we may feel that our health could use a bit of a boost.

So, a great way to get back on track and give yourself a kickstart into the new year is with intermittent fasting (IF).

Through February the team here at Lane Cove Chiropractic will be doing a 28 day “Fast Start” Intermittent Fasting Program and we invite you to join us.

We will be providing you with more information over the coming weeks on how to do this style of fasting and the many health benefits, backed by science, that it can provide.

Let us know if you’re interested and we’ll pop your name on a list of potential participants.

(The information on IF and the science supporting it is taken from the Zoe Science and Nutrition Website)


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