Grabbing the 5:2 Fasting bull(shh) by its horns!

One of the diets taking over the nation right now is intermittent fasting.

The whole 5:2 day thing!

What is that you may ask?

In all simplicity, fasting two days in a week for longer life, better insulin responsiveness and weight loss.

Ahh so simple!

Does intermittent fasting work?

Anyone fasting twice a week would consume much less energy on a ‘’fast’’ day compared to the day they would eat normally. This deficit in energy would obviously result in some weight loss. Assuming you are not eating extra on your non-fasting days, it will be surprising if you didn’t lose weight. Duh!

Is there any evidence that intermittent fasting aids weight-loss?

One of the most recent pieces of research on intermittent fasting is a 2012 study (PDF, 291.4Kb), which recruited 30 obese women.

After an initial two-week period they were then given a combination diet of low calorie liquid meals for six days of a week (similar to Slim Fast diet products) and then asked to fast for one day a week (comsuming no more than 120 calories).

After eight weeks, on average, the women lost around 4kg (8.8lb) in weight and around 6cm (2.3 inches) off their waist circumference.

But let’s break this study down, shall we?

  • These women may have had increased motivation to stick with the diet because they knew their weight would be monitored (this is a psychological effect that slimming clubs make use of, they are being watched, like the biggest loser).

  • The follow-up period was short – just two months. It is not clear whether this diet would be sustainable in the long-term or whether it could cause any side effects.

  • 30 people a very small sample size. A much larger sample – including men – is required to see if intermittent fasting would be effective in most overweight or obese people.

What is going to happen if you continue fasting?

Fasting for weight loss is counter-productive. Consuming too few kilojoules will make your body think it is starving and will then adjust your metabolism. When you go back to eating normally, your metabolism won’t readjust and therefore you will need fewer kilojoules than before, so you swing between losing weight and putting it back on again! What's worse, weight loss during a fast is usually a combination of fat, fluid, and muscle, but the weight that you gain back will most definitely be all-fat.

Why you shouldn’t fast?

Come on guys, fasting is difficult! The days you are fasting, I guarantee you will speak of an intense, unrelenting hunger and feel food obsessed and constantly think about food to the point of distraction. You will not be able to concentrate on your daily work and will be reaching for that packet of Tim Tams (quite a picture I painted aye?).

Think about fatigue! There is a massive dip in your energy on the 2 days of food abstinence right? Every animal (rat) experiment conducted shows that they are lethargic on a calorie restriction diet and can barely do anything. Humans, obviously will feel the same.

On the other 5 days, you are more likely to binge my friends. You are putting yourself up to developing an eating disorder with this kinda yo-yo dieting screwing up your metabolism.

Take home message

Follow a healthy, balanced meal plan with plenty of vegetables, fruit, lean proteins, whole grains, and other nutrient-dense foods for a more long lasting and sustainable eating lifestyle.

For more information on healthy eating, contact a Registered Dietitian who can provide expert nutritional advice tailored to your individual requirements.