It’s on everyones lips at the moment. Intermittent fasting (IF) has gained significant popularity the last few years, situating itself as one of the worlds most popular health and fitness trends.

But is there truth behind the claims, or is it just another fad? Today we explore the interesting world of IF!

IF, also sometimes referred to as time restricted eating, is an eating pattern that encourages cycling between periods of eating and fasting.

It’s (arguably) not a diet in a conventionally agreed manner; as it isn’t about what you eat, but rather the timing of eating - and so you don’t have to remove certain food groups or consciously restrict calories (exempting the 5:2 method - more coming below), making it more of a ‘lifestyle’ and far less all-consuming!

Historically, humans have fasted naturally for thousands of years. Back in hunter gather times when food was sometimes scare, and supermarkets and refrigerator were only something of the future, it wasn’t uncommon to experience periods of feast and famine.

In religious and philosophical contexts fasting has been, and still is, an important ritual, with many major groups practising periods of fasting; including Islam, Judaism, Hinduism, Buddhism and Christianity.

Due to the popularity of IF, a number of methods have been devised. Here are some of the most common methods of approaching IF:

  • The 16/8 method aka fast for 16 hours each day: often toted the most simple and sustainable to implement. 16/8 is where eating is restricted to an eight hour window each day i.e. eating between the hours of 11am - 7pm, and then fasting between 7pm - 11am.

  • The 5:2 diet aka fasting for two days each week: where you consume 500-600 calories on two non-consecutive days of the week, and then eat normally for the remaining five days. For context, this equates to about a quarter of your typical daily energy needs.

  • Eat-Stop-Eat aka do a 24/hour fast once or twice a week: although also popular, 24 hours of fasting may be too much for some people.


This is when things get really interesting. When we fast many things begin to happen beneath the surface on a cellular level.

As we don’t have food, aka energy, coming in our body will adjust hormones so that fat mass utilisation for fuel becomes more readily available.

One of these is insulin which helps control blood sugar levels. IF may improve insulin sensitivity and lead to hormone levels dropping dramatically, making body fat more accessible.

Certain genes are also turned on that tell cells to switch into preservation mode, where they become more resistant to cellular stress and frugal with resources, as shown in lab studies with mice.

Cells also begin important repair processes. The includes the phenomena autophagy (au-toph-a-gy) where they begin to digest and remove older and dysfunctional proteins, aka unwanted and unneeded cellular material, as well as fixing up damaged parts - a little like taking a car in for a service!

IF has been shown to combat inflammation, through the reduction of inflammatory markers associated with CVD, as well body fat. Leading to…


IF is often toted as an effective tool to promote weight loss, and a common reason it’s often explored.

When attempting IF, no matter the approach, there will be an element of skipping meals/food when fasting - and through the reduction of meals, there’s naturally a reduction in overall calories eaten.

But don’t just take our word on the weight-loss front - there is research to back its efficacy in doing so. A 2014 review study found IF caused a 3-8% reduction in weight-loss over the period of 3-24 weeks, holding significance over other studies on weight-loss. Interestingly, and in the same study, it was associated with a loss 4-7% of waist circumference - an area where we’re prone to storing harmful belly fat.

As a strategy to weight-loss, IF has shown it may be more effective in retaining precious muscle mass; compared to the common approach of evoking a daily overall calorie restriction with no change to eating pattern. When we lose weight, we lose both fat and muscle - the latter not so ideal.


This success comes from eating fewer calories. If you overeat/indulge during an eating period, you may not experience the same results.



Like everything - there’s two sides to the coin. IF may lead to some sensations of hunger, which might impact concentration or energy; although this may only be temporary as the body adjusts to a new way of eating.

While considered to be overall very safe to conduct, IF isn’t a magic bullet. It’s not for everyone, and in some cases may be harmful and should be avoided. It’s always best to chat with a medical or health professional first to discuss whether it’s right for you - this includes, but isn’t limited to:

  • Those with disordered eating or eating disorders, or a history of.

  • If you’re underweight.

  • If you’re taking certain medications.

  • If you have a health issue like diabetes, low blood pressure, or issues with blood sugar regulation.

  • If you’re trying to fall pregnant, are pregnant or are breastfeeding.


Some evidence has shown IF may not be as beneficial for women over men. With only animal-based studies available, IF has shown to improve insulin sensitivity in male rodents, but worsen blood sugar control in female rodents as well as negativity impact the females reproductive cycle due to a food deficient environment. While this may not be true for all women, and some may really enjoy IF, it’s definitely good to keep in mind.

This blog was written especially for our friends at Westpac NZ, who we’re excited to be assisting with their workplace wellbeing this year. It’s thrilling to see a company go the extra mile for their staff!