Early results from studies investigating this unique dietary approach, said to mimic the "feast and famine" lifestyle of hunter gatherers, are promising.

While short-term in nature only, blood pressure, cholesterol, blood glucose and insulin levels appear all to benefit significantly from regular periods of low-calorie eating, as does weight, with advocates reporting safe and sustainable weight-loss results from the data currently available.

So, it sounds easy - cut back on your calories, right back, on just two days a week and shed the kilos? In theory, yes, but in reality it may not be so easy for everyone.

Diets of 500-600 calories mean that you will not be eating very much. For example, 500-600 calories spread over two meals equates to one poached egg on a small slice of wholegrain toast, a piccolo coffee in one meal and just 80-100 grams of fish and vegetables or salad in the other. For non-eaters, such as busy businessmen or shift workers, this may not seem that extreme but for the average person, who tends to eat several times a day, such an enormous shift in eating habits may not prove that easy, particularly in social situations.

My experience is that followers tend to eat more like 800-1000 calories a day while fasting, as an extra coffee or snack slips in, which unfortunately negates the benefits of the "fast".

The second issue when individuals adopt diets that are restrictive in nature is that psychologically it can prime us to think about food more and more.

In this context, the simple act of aggressively restricting calories, especially after a lifetime of being "on" and "off" various diets, triggers the deeply entrenched thoughts that accompany the start of yet another diet.

In this instance, the mere notion of being restricted, even for a very short period, is enough to drive individuals to think about food, or rather the lack of it, more and more, makes it almost impossible to maintain long term.

Another crucial point when considering a regular fast in your weekly dietary regime is what your energy demands are like.

If you sit down in front of a computer for many hours each day, and are not overly interested in food, cutting back for a couple of days is unlikely to cause any major issues.

On the other hand, if you are a busy mum with three kids and you go to the gym every day, chances are cutting your calories back that much when your energy demands are high may leave you feeling tired, irritable and battling extreme hunger and cravings, even if it is just for a day in total.

As is the case with any diet, no matter how positive the results are reported to be, it's important to make sure it is sustainable and, most importantly, doing no damage.

So, if you know that your body and metabolism will benefit from such an extreme diet kick start, by all means, give the 5:2 diet a try, but make sure you do it right - just 500-600 calories a day in total.

But if cutting back calories so aggressively is too extreme, try cutting back a little: drop the snacks, have a smaller portion of dinner and have a salad for lunch. You may be surprised to find that you can also lose a few kilos just cutting back slightly, every single day.

SMH