Can intermittent fasting help you lose weight?

Intermittent fasting has topped the diet trends for several years spurred on by celebrity converts and new reincarnations of the diet. We explore everything you need to know before you miss a mouthful of food.
 

WHAT IS INTERMITTENT FASTING? 

There are a lot of diets that now fall into the category of intermittent fasting including the high profile 5:2, the newer 16:8, Eat Stop Eat, the Warrior diet and alternative day fasting.

The 5:2 diet hit the headlines thanks to British journalist Dr Michael Mosley and his New York Times bestseller The Fast Diet. This style of intermittent fasting includes eating normally for 5 days a week and dramatically limiting calories for two days a week.

The aim is to drop caloric intake on fasting days to just 25% of the norm. So, if on average you ate 8,700 kilojoules (2,000 calories) a day, on fasting days this would be limited to 2,000 kilojoules (500 calories).
 
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We’ve since seen rise of the 16:8 diet. In this case, the numbers refer to hours - eat what you like for 8 hours a day and fast for 16.

Eat Stop Eat requires fasting once or twice a week, while alternative day fasting takes it up a notch to fasting, or eating minimal calories, every second day.

The Warrior Diet may be the most controversial and extreme of all styles of intermittent fasting. Created by Ori Hofmekler, a former member of the Israeli Special Forces, the diet focuses on undereating or “fasting” for 20 hours a day and then eating as much food as you like for a 4-hour window at night. During the 20-hour fasting period, you can eat small amounts of dairy products, hard-boiled eggs and raw fruits and vegetables, and are encouraged to drink a lot of fluids (that contain no calories, of course).
 

BUT DO THESE DIETS WORK? 

In our fast-paced lives where many of us eat on-the-go and can be guilty of snacking constantly, intermittent fasting forces us to put on the brakes and allows our bodies to use up some of our fat stores. Several studies show that intermittent fasting can help with weight loss, primarily through restricting the hours in which a person can eat, reducing the amount of food that is consumed and therefore overall energy intake. It’s really a change of when to eat, rather than what to eat.

While intermittent fasting can help with weight loss, overall research shows that it is no more effective or beneficial in the long term than general healthy eating and calorie restriction. For most people, it is better (and easier) to stick with a well-balanced, plant based diet.
 

WHAT’S THE BEST WAY TO TRY INTERMITTENT FASTING?

Choosing when you fast can make a big difference. There’s a ton of evidence that eating breakfast helps regulate your appetite, manage your weight, bump up your nutrient intakes and also helps with cognition - it makes sense that your body needs fuel especially after breaking the fast.
 
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So don’t fall into the common trap of skipping brekkie if you want to give intermittent fasting a try. Load up early in your eating window to help stabilise your blood sugar levels and manage appetite control.

If you are thinking about dropping a meal all together or cutting back on your food intake on certain days, try it at dinner, as evidence consistently shows that we have better insulin and glucose control during the day compared to the evening.
 

WHAT ARE THE PROS AND CONS OF INTERMITTENT FASTING?

Pros 
  • One reason for the growing legion of 16:8 fasting fans is that you can forget calorie counting. This style of intermittent fasting does not involve fixating about what you eat, just when you eat.
  • Advocates of intermittent fasting also say that it can provide benefits that may extend beyond weight loss. Early studies with animals suggest alternative day fasting may help lower the risk of certain chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. However, to date, there’s been no extensive studies in humans, and more research is needed before we can say whether intermittent fasting has benefits other than weight loss.

Cons
  • One of the biggest pitfalls of an intermittent fasting diet is sticking to it. Fasting is hard, even if it is only for two days a week. Researchers have even noted high drop out rates on fasting diets.
  • In addition, intermittent fasting, like many other restrictive diets, can lead to certain nutrient deficiencies. Anyone considering fasting should first discuss it with a doctor and dietitian to make sure that they are getting enough nutrients from their diet.
  • There are also certain people which intermittent fasting is not recommended for, including pregnant or breastfeeding women, individuals with a history of disordered eating, and people taking medication that is dependent on food intake e.g. diabetes.


CAN YOU EXERCISE WHILE FASTING?

If you’ve Googled intermittent fasting, there’s no doubt you will have seen stories of the battle to manage fasting with a regular exercise routine. Certainly, some people struggle to exercise when fasting, noting increased fatigue, muscle loss and difficulty recovering.
 
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It’s important to plan your exercise based on the intermittent fasting diet you are following. If you’re on the 5:2 diet, plan your big sweat sessions for non-fasting days and line up light exercise, or rest days, for fasting days.

If you’re on the 16:8 diet, plan your exercise for your 8-hour eating window and what works best for your body. Some people prefer to work-out on an empty stomach, while others need to fuel up first. There’s also evidence to show brekkie before burpees can help burn more carbohydrates through the day.

Either way, try to include protein after exercising as part of the 8-hour eating window. Aim for 20-25 g of protein after exercising for muscle growth, tissue repair and recovery. And don’t forget to stay hydrated!

If you’re considering intermittent fasting, chat to your doctor or a dietitian before making a start.

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