The experts on intermittent fasting

It’s recognised as one of the most effective diets for weight loss. Our senior dietitians explain how intermittent fasting works.

What you need to know

Intermittent fasting eating plans are all about having a break, in which you give your body a rest from digestion. The idea is for your body to have some downtime from food.

There are many variations of this food plan. There’s the popular 5:2 diet, where you eat normally for five days and restrict yourself to just 500 calories for the remaining two, which is great for socialites who can’t diet every day. There’s also the 16:8 diet, where you eat whatever you want for 8 hours of the day then fast for 16 hours, which sounds easier than it actually is. There are other variations like the 12:12 method and plans where you stop eating in the early afternoon, aiming to consume your kilojoules earlier in the day for better weight loss.

If you’re open to giving intermittent fasting a crack, here are some pros and cons to consider before you go ahead and book your fast days. 


  • You’ll probably lose weight, but it will most likely be due to kilojoule restriction. Most of the emerging science has found that people who lost weight by fasting probably did so because they were eating less kilojoules overall, rather than because of the fasting itself.
  • If you start your fast earlier in the evening you’ll be eating more during the day and less at night when your body doesn’t need as much energy. This is a bonus, as your metabolism slows in the evenings. Insulin production also increases at night, so if you eat late at night, your blood glucose is likely to be much higher and you won’t burn off kilojoules as effectively.
  • You’re giving yourself a cut-off time to stop eating. Think of it as “the store is closed” when you feel like reaching for those moreish peanut M&M’s while you watch TV.


  • You’re going to get hangry. Really hangry. Particularly with diets like the 5:2 where you can only eat 500 calories a day. This is the equivalent of two boiled eggs and a grilled tomato for breakfast, a can of tuna in springwater with lettuce leaves for lunch, 100g poached chicken and steamed broccoli for dinner and a small tub of yoghurt.
  • If you try the 16:8 approach and fast for a long period of time each day, your blood sugar levels might drop and you could find yourself wanting to binge on anything you set your sights on.
  • Intermittent fasting diets are difficult to maintain, and time-restricted eating is hard to fit into a social life. Ask yourself if this diet is really going to fit into your social calendar.

If you’re wondering if intermittent fasting is right for you, consider what your goals are and what your lifestyle is like. Are you the kind of person who needs a solid brekkie, lunch and dinner plus snacks to keep you going? Would you be prepared to feel a bit off for a couple of days a week because your brain doesn’t have the fuel it’s used to having?

Find out what works for you, but remember that getting ripped and sustaining a diet only works when you make a complete lifestyle change. You’ve got to make sure that whatever you sign up to do, it’s going to work for you in the long term.

Jemma O’Hanlon
Accredited Practising Dietitian & Nutritionist



Going ahead with it

So you’ve decided you want to try intermittent fasting. Here are some tips on how to begin working a fast into your day.

1. Limit your eating hours

While research is in its early stages, studies have found real benefits associated with not eating for at least 12 hours overnight. So if you decide to take the 16:8 approach or go for the easier-to-maintain 12:12 method, the best results will be achieved if you develop a regimen that works for you and stick to it.

2. Eat 2-3 substantial meals

Intermittent fasting naturally controls calorie intake without needing to drastically constrict portion sizes, but it also means you’ll need to eat substantial balanced meals that will keep you satisfied for several hours. This means a filling breakfast, a generous lunch and a regular dinner — no need to cut back on the calories. But this doesn’t give you an excuse to binge. Have a meal that you feel like and which will satisfy you.

3. Focus on the evenings

One of the common themes of all intermittent fasting plans is that they stop food consumption relatively early in the evening. Research has shown that simply having your last meal a little earlier can help you lose weight. The earlier you stop eating the better, but aim to finish your final meal by 8pm at the latest.

4. Don’t count calories

While we’re still learning about the intricacies of intermittent fasting, overly restricting calories while limiting your eating times doesn’t work. You’ll naturally eat fewer calories on an intermittent fasting plan and gain a metabolic boost by eating over fewer hours each day. You won’t get the same results if you also further restrict your calories.

Susie Burrell
Accredited Practising Dietitian