Skip to main content

What is the go with fasting?

You may have heard of a relatively new weight loss trend, called intermittent fasting, IF, the 5:2 diet… there are a few names flying around. So what does this type of fasting entail, and what does it do to the body?


Essentially, fasting decreases the amount of calories that you consume over the course of a day, or over the course of a few days in a week. Intermittent fasting, or IF, uses an 8-hour window of eating. This means that from 11am-7pm, or 12pm-8pm (any 8-hour window you like), you can eat. There is no eating outside of this time period. This also includes drinks such as smoothies, juices or anything with calories. Water and black coffee or tea is allowed outside of these time periods. This can be relatively easy for some people. However, people who work long hours, or have demands early and late at night may find adherence difficult due to the lack of consistent energy being supplied to the body.


The 5:2 diet is a little different. Over the course of a week, for five days eating is normal, but there are two “fasting days” in there (separated by at least one day). These two fasting days are when food intake is cut down significantly, and requires a person to only eat 500-600 calories (around 2,000-2,500 kilojoules). This is the equivalent of around two slices of plain bread (no spreads!), two eggs, an apple and a small tub of plain yoghurt.


Fasting can decrease the overall energy intake over the course of a day, or two days in a week. The “science” behind it is that the body does not go into starvation mode as there is still enough food being consumed during those 8-hour windows, or on the five normal eating days. It is more of a lifestyle choice, rather than a diet, as it is about eating times, not restrictions on certain foods.


There are pros and cons to intermittent fasting. It can help lower overall energy intake, which promotes weight loss, it is easy to follow and stick to (not restricting or cutting out whole food groups), can assist in resetting hunger cues and help manage blood sugar and blood lipid levels. However, it can also cause fatigue and dizziness, can cause restricted eating and sometimes, it doesn’t do anything at all! When using 8-hour intermittent fasting, if you still consume the same amount of calories in that time period that you would in an entire day, there would not really have been any benefit to restricting your eating time frame. If energy-dense or foods higher in saturated fat are eaten during these time periods, then overall the body will still not be receiving the nutrients it needs.


Studies on the long-term benefits of intermittent fasting have not yet been concluded, so it is hard to say what the affects are going to do to the body long term. However, adhering to a fasting diet, if it is safe to do so for you as an individual, can be a great strategy in weight loss. Discussing this with your dietitian is a fantastic idea, to ensure fasting is done with the proper supports in place.