Lauren Travers

Something that you all will have heard about, and many of you may have tried is fasting. Whether it be 24 hour fasts, intermittent fasting, water fasts, juice fasts, 3-day fasts, morning fasts etc, the principles and goals behind each are similar in nature.

So let’s discuss the variations of fasting, why it is beneficial, the side effects associated and whether or not it may be for you.


What is fasting?

Fasting is the elimination of solid food for a chosen duration of time. Water is generally still permitted during a fast, but not always. The time and variation of fasting depends upon the desired outcome, and the reason behind undertaking the fast. For example, prior to some blood tests and medical procedures, you are required to ‘fast’ from all food for a 12 – 48 hour window leading up to the event. This is to ensure that your blood sugar levels and other system levels are at their natural, unaltered state in the case of blood tests, and to ensure that there is no food in the digestive tract which may be eliminated during a medical procedure. These fasts are prescribed by a doctor, and must be adhered to strictly.

However, aside from medical related fasts, you may have heard of many other variation now emerging with claims to improve health, restore vitality, improve mental cognition, ‘detox’ or cleanse the system as well as cause significant weight loss. Some of these include:

  • Intermittent fasting – popular amidst dieters and those wanting to lose weight, intermittent fasting is the implementation of structured ‘fasting’ and ‘feeding’ windows throughout your day. The most common of these is the 16:8 which allows for an 8 hour eating window (during which you can consume as much food as you like without counting calories) followed by a 16 hour fasting period where you are allowed nothing but water, herbal tea and plain black coffee.
  • 24 hour fasts – Coined for it’s myriad of health benefits, the 24 hour fasts are to be included once or twice per week to allow your body a rest from the ‘strenuous’ and energy consuming process of digestion. Whilst popular amongst dieters and health gurus alike, it claims to improve your system efficiency, boost metabolism and mental cognition, and stimulate weight loss. Research from Medical journalist R, Collier suggests that occasional 24 hour fasting can improve cardiovascular health. Some evidence from research on animals shows that fasting can help fight certain kinds of cancer or even help preserve memory.
  • Juice fasts, lemon water fasts, detox fasts – A much newer addition to the fasting world, these fasts involve only consuming a specific drink or certain foods during the fasting period of up to 3 days. Sometimes whole food groups are eliminated, cooked foods, or all solid foods. The weight loss achieved from these sorts of ‘diet’ fasts is often short-term, and there is no conclusive evidence to prove the efficiency in detoxification of the system.
  • Calorie Restriction – calories are heavily restricted for certain days of the week. A popular diet which takes this approach is Dr Michael Mosley’s 5:2 diet whereby you eat normally for 5 days of the week, and then consume only 500 calories on the other 2 days.


Fasting for Health

Many studies have been done which confirm the powerful benefits of fasting in improving your bodies system efficiency, and long-term health.

In an online article by Healthline, 8 Health Benefits of Fasting backed by Science there are links to comprehensive scientific studies which back a myriad of health benefits from both long duration (24-72 hr) fasts as well as intermittent fasting. Some of these benefits include Reducing insulin resistance, fighting inflammation, Improving Blood Pressure, Triglycerides and Cholesterol Levels, preventing neurodegenerative disorders, stimulation growth hormones and boosting metabolism. You can read more about those studies here.

Whilst these benefits sound so good you’re probably ready to quit eating right this second, please note that results vary greatly from person to person, and depending upon your current level of health it may not be advisable to undertake a fasting regime. Ensure you always consult with your GP or a registered dietitian prior to undertaking a fast.


Fasting and Weight loss

Whilst ‘intermittent fasting’ is the new buzz word amongst weight-loss communities, it’s results may not be as clean cut as you think. The predominant reason that people lose weight on a fasting diet, is simply because they consume significantly less calories than they would consume in a larger fasting window. Fewer calories = weight loss. You need a deficit of 14644 Kilojoules to burn 0.5 kgs of fat. So in order to lose half a KG each week, you would need to reduce your daily energy intake by 2000Kj. If you are reducing the period of time that you ‘eat’ from 14 hours down to 8 hours, that is 6 whole hours less energy than you would normally consume. This is why intermittent fasting can be beneficial to weight loss, not the act of fasting itself.

The main downside to intermittent fasting is its mental and social isolation, as well as the emphasis on restriction. This can be counterproductive to healthy mind sets around eating well, and also very difficult to maintain over long-term duration.

As published on Jama Medical Network, a recent study by K Trepanowski showed people with obesity who fasted intermittently for 12 months lost slightly more weight than those who dieted in a more traditional way, but the results were not statistically significant. For example, the same study found that people who fasted were more likely to give up on weight-loss efforts than those who dieted in a more traditional way, such as counting calories. The researchers concluded that fasting might be harder to maintain over time.


Are there risks to fasting?

The simple answer is, yes. For many people, fasting is not only ineffective, but can also pose a significant risk to their health. Examples of such include:

  • people with diabetes
  • people with a history of eating disorders
  • people using medications that they must take with food
  • children and adolescents
  • those who are pregnant or breastfeeding

Whilst fasting for short periods is generally safe, it should always be done under the guidance and supervision of your doctor, or a registered dietician.

Aside from the health related risks, there can also be some backlash to fasting when it is done in a weight loss setting. The predominant one is post-fast bingeing. After a prolonged period of deprivation and limitation, it is quite common to ‘lose control’ when it comes to eating again. This can lead to binge eating to the point of illness, which is often followed by feeling of guilt, remorse and regret. None of these feelings will help you to maintain the positive outlook which is paramount to healthy weight loss.

Another potential side effect of long term fasting is a slowing of the metabolism. Particularly in cases where individuals also limit their food intake or count calories during the period of eating. A severe deficit in daily calories will cause your body to go into a ‘starvation mode’ whereby it slows down body functions (including digestion of food and conversion into energy) in order to ‘save’ its energy for vital bodily functions (organ function, cell regeneration). Over a prolonged period, this aggressive fasting will cause your Basal Metabolic Rate to slow down significantly, meaning your body can process less energy, you will physically HAVE less energy, and you are more likely to store excess fat as a result.


So is fasting really the right approach for you?

As a general rule, I do not promote fasting to the majority of my clients. Reason being, when an individual reaches out for help with their nutrition, it is often because they do not have a ‘healthy’ relationship with food. The predominant goal is to work on improving, and strengthening this relationship and  In my experience, extreme and restrictive measure like fasting only work to further exacerbate the problem.

From a ‘health’ perspective, the evidence backing the benefits of fasting is conclusive, and certainly worth considering if you are of a healthy weight and disposition. However, when it comes to weight loss, the backings are inconclusive, and certainly not guaranteed.


A more moderate approach …

If you are considering fasting, and would like to benefit from the positive health improvements that fasting may offer then why not try this more moderate approach.

Each night, ensure that you have a minimum of 12 hours between your last, and first meal. Ideally you can build this up to 14 hours to gain maximum benefit without having to fall into a restrictive or limiting behaviour pattern.

For example, if you eat dinner at 7pm, do not consume anything aside from water and non caffeinated herbal tea until at least 7am the next morning. Try to build this to 9am. Sounds easy, right?

Studies have shown that the benefits of fasting begin around 8 hrs after last consuming food, so 12-14 hours is giving your body a good amount of time in this fasted state. Adopting this fasting period overnight whilst you sleep not only makes it easier to stick to (you cant feel hungry whilst you’re asleep) it also helps to reduce/eliminate late night mindless snacking, and reduces your overall calorie window for food consumption which will eventually lead to weight loss. As your body will not have to waste energy on digestion whilst you are sleeping, it can invest more of its energy into repairing damaged cells and creating new tissues, meaning a better quality of sleep for you, and a better performing system the following day.

The health benefits of fasting, without the associated risks and downfalls! Sounds like a winner to me!


About The Author

Lauren is a qualified nutritionist with a passion for holistic living and mindfulness.  She believes that health starts from what‘s on your plate, and the way that we ’think’ about food. “Our state of mind is the biggest enemy when it comes to changing our bodies” says Lauren. “There is no quick fix. We need to look at the body as a whole, and try to regulate any imbalances whilst targeting negative thought patterns.”

Lauren’s passionate about educating clients on how to nourish their bodies back to health and create a balanced relationship with food. She specialises in women’s health, weight loss, sports nutrition, and food intolerances.



Healthline, (2019), 8 Benefits of fasting backed by science, retreived from URL

Trepanowski, Kroeger, Varad. (February 26, 2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. Retreived from URL

Collier, R. (June 11, 2013). Intermittent Fasting: The science of going without. Retreived from URL