What is intermittent fasting and how does it work?

Short answer: Intermittent fasting is an eating plan that alternates phases of eating with set intervals without eating any food (fasting) on either a daily or regular basis, ranging from a few hours to fasting for a whole day.

Long answer:

Intermittent fasting is the process of only eating within a specific timeframe as a means to improve your health and metabolic output. Fasting for a certain number of hours each day or eating 500-600 calories a few days a week can assist your body in metabolising carbohydrates in your body and begin to oxidise (burn) fat.

There are several different ways to intermittently fast, with all approaches based on choosing regular and consistent time periods to both eat and fast. Some of the different methods that are currently popular are below.

1. The 5:2 Diet – This method focusses on limiting your intake to 500 calories per day for two days a week. During the other five days of the week, the goal is to maintain a healthy and balanced diet.

2. Alternate day fasting – This involves “modified” fasting every other day, e.g. limiting your calories on fasting days to 500 – or 25% of your normal intake. On non-fasting days, aim to resume your regular diet approach.

3. Time restricted eating (16/8 or 14/10 method) – The idea is to set fasting and eating windows based on preferred or available eating times. A 16/8 approach would require you to fast for 16 hours of the day, then only eat within an 8 hour period of the day, ensuring you maintain your hydration levels throughout the day.

4. The 24 hour fast – This involves fasting completely for a full 24 hours. Often times it is only done once or twice a week. Most people fast from breakfast to breakfast or lunch to lunch. The downside to this method is the side effects can be extreme in some people, such as fatigue, headaches, irritability, hunger and low energy.

Intermittent fasting or restricted eating is not a new idea and is regularly seen in many religious cultures in the form of Ramadan or Lent. There are many reported benefits to intermittent fasting, such as weight loss, reductions in blood pressure and improvement in markers of metabolic disease risk.

From about 3-8 hours into a fast, the blood glucose level is maintained by the liver breaking down glycogen stores into available glucose for the body to use. To keep up with the body’s metabolic rate, triglycerides are then broken down into free fatty acids, becoming a fuel source for muscles.

Intermittent fasting is safe for many people but is not for everyone. Prolonged timing between meals may not be the best way to manage your weight if you are pregnant or breastfeeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical conditions, it is advisable to see your regular GP first.

If you are confident that you can trial an intermittent fast, our Dietitian Andrea Kunneke can help you with a healthy eating plan and guide you through your choice of fast.

Here at WLC Medical, Nurse Practitioner Julie McLean of Perth Paediatric and Family Clinic can also assist you with an appropriate health check to determine your eligibility for intermittent fasting.

Like with any approach, consistency is key, as the body can then best adjust with a reduced risk of any adverse effects. Once fasting times can be established that suit your body clock, daily schedule and health, it may need time to adjust and settle into your new routine.

Setting up an intermittent fasting approach in terms of a SMART goal (Specific, Measureable, Attainable, Relevant, Timed) is recommended to best determine your plan of attack. From there, once you have a good enough ‘why?’ in trialling your approach that’s important to you, you’ll then have the fuel to follow through with your ‘how’.