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Intermittent fasting 101

Intermittent fasting 101

While we know that all you need for a ‘beach body’ is a body that you take to a beach, there’s no doubt that summer is a time when many of us want to shed a few pounds.

In the endless quest to control the calories, the intermittent fasting (IF) technique is a popular front runner. So what is IF and does it work?


IF involves days of normal eating interspersed with ‘fast’ days of extremely restricted calorie intake. On ‘fast’ days the dieter should eat no more than 25% of their normal calories. For most people this is about 500-600 calories.

The 5:2 pattern is the best known form of IF, with the two fast days being non-consecutive. Another variation is alternate day fasting (ADF) which advocates no restrictions on eating on normal days.

There are also daily variants which limit the times when eating is allowed.


The NHS has summarised various studies and reviews into the effectiveness of intermittent fasting. There have been no universally recognised clinical studies. There is also no conclusive evidence that the time at which you eat makes any difference to how calories are handled.

However, many believe that the ‘feast-famine’ model is how human beings are designed to live, going back to our hunter-gatherer days. Hence IF is simply working with the natural rhythms of our bodies.

Perhaps the simplest answer is that the heavy restrictions on fast days lead to an overall reduction in calorie intake. So IF is a structured way of eating less, and that may be why it works for many people.


Some people find that hunger on the fast days affects concentration, efficiency and reaction times. So fasting is not compatible with demanding jobs or driving. Hungry people can also be grumpy, so fast days can be a risk to relationships. If you're looking for an alternative fasting approach that is guaranteed to have ZERO risk, you could try this reversed water fasting trick.

Food and eating should be part of the pleasure of life, but a long-term regime such as IF may mean that food starts to rule life. Keep a sense of proportion (and don’t be a diet bore!)

IF is not suitable for diabetics, pregnant women, children and people with other long-term health conditions.


The top tips to make IF work are:

  • Keep the ‘normal’ days sensible – they are not a licence for a blow out!
  • Ensure that fast days have filling balanced meals. This reduces the chance of over-eating.
  • Don’t let it rule your life.

IF could well be a good way to kick start a lifestyle change. We know that we need sensible eating and regular exercise – keep an open mind, look after your health and see what works for you.


the author

Jessica Ambrose

Jessica is a fitness writer who loves long distance running, yoga, strength training and healthy eating.