Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. Unlike most diets, it doesn't tell you what to eat so much as when to eat it. The approach has grown rapidly in popularity among Australians seeking a flexible, evidence-informed way to manage their weight and general health, and it has attracted significant research attention over the past decade.
What intermittent fasting actually means
At its core, intermittent fasting is about structuring your eating within defined windows of time. During fasting periods, you consume little or nothing beyond water, black coffee, or plain tea. During eating windows, you eat normally, without necessarily counting calories or cutting food groups. The theory is that giving your body extended breaks from food encourages it to shift from burning glucose for energy to burning stored fat, a metabolic state sometimes called ketosis.
This isn't a new idea. Humans have fasted for centuries, whether for religious reasons, cultural practice, or simple necessity. What's new is the structured, evidence-backed application of fasting cycles as a deliberate health strategy.
The most common methods
There are several popular approaches to intermittent fasting, and the right one depends heavily on a person's lifestyle and goals.
- 16:8 method: You fast for 16 hours and eat within an 8-hour window each day. A common version is skipping breakfast and eating between midday and 8 pm. This is the most widely practised form.
- 5:2 method: You eat normally five days a week, then restrict calories to around 500–600 on two non-consecutive days. It's more flexible than daily fasting but requires discipline on restricted days.
- Eat Stop Eat: A 24-hour fast once or twice a week, from dinner one night to dinner the next. More intense, and not recommended for beginners.
- Alternate day fasting: You alternate between regular eating days and fasting or very low-calorie days. Research suggests it can be effective but many find it difficult to sustain.
- The Warrior Diet: A 20-hour fast followed by one large meal in the evening. Based loosely on ancient eating patterns, it suits some people but is quite restrictive during daylight hours.
What happens in your body when you fast
When you stop eating, your body works through several stages. In the first few hours after a meal, blood glucose and insulin levels drop. Once glucose stores in the liver (known as glycogen) are depleted, usually after around 12 hours, the body begins breaking down fat for fuel. Alongside this, cellular repair processes called autophagy become more active. Autophagy is essentially the body's way of cleaning out damaged cells and regenerating new ones, and emerging research suggests it may play a role in reducing inflammation and supporting longevity.
Insulin sensitivity tends to improve with intermittent fasting, which is particularly relevant for people at risk of type 2 diabetes. Some studies have also found modest reductions in blood pressure, LDL cholesterol, and inflammatory markers, though the evidence base is still developing and results vary across individuals.
Is intermittent fasting suitable for everyone?
Intermittent fasting is not a one-size-fits-all approach. Most healthy adults can try it safely, but certain groups should consult a doctor or dietitian before starting. This includes people who are pregnant or breastfeeding, those with a history of disordered eating, people managing diabetes or blood sugar conditions, and anyone on medications that require food for absorption.
It's also worth noting that the benefits of intermittent fasting are closely linked to overall diet quality. Eating highly processed foods within your eating window will blunt most of the potential gains. Pairing intermittent fasting with a balanced diet that prioritises whole foods, fibre, and lean protein gives the approach its best chance of working.
Intermittent fasting and gut health
One area of growing interest is the relationship between fasting cycles and the gut microbiome. Research suggests that giving the digestive system extended rest periods may support microbial diversity and reduce inflammation in the gut lining. For Australians already paying attention to gut health, intermittent fasting may complement other dietary strategies aimed at supporting beneficial bacteria.
That said, abrupt changes to eating patterns can initially cause digestive discomfort, headaches, and fatigue as the body adapts. Most practitioners recommend starting with a shorter fasting window, such as 12 hours, and gradually extending it over several weeks.
Common myths and misconceptions
A persistent concern is that fasting causes muscle loss. The evidence suggests this is minimal, particularly in people who maintain adequate protein intake and include resistance exercise in their routine. Another myth is that skipping breakfast is inherently unhealthy. Breakfast timing only matters in the context of your total nutritional intake and daily rhythm. There is no universal rule that breakfast must be eaten in the morning.
Some people worry that intermittent fasting will leave them constantly hungry. In practice, many find that hunger signals adapt within a week or two. Hormones like ghrelin, which drive hunger, tend to shift to align with your new eating pattern over time.
Getting started practically
If you're considering intermittent fasting, a gradual approach works best. Start by pushing your first meal one to two hours later than usual and pulling your last meal earlier. Increase the fasting window by an hour every few days until you reach your target. Stay well hydrated during fasting periods, prioritise sleep, and pay attention to energy levels and mood rather than just the scales.
Intermittent fasting is a tool, not a cure. It works best when it fits naturally into your existing lifestyle rather than fighting against it. Some people thrive on a 16:8 schedule; others find the 5:2 approach more sustainable around social eating and work commitments. The best method is the one you can maintain consistently without significant stress or disruption to daily life.