04/03/2016 5:40 AM AEDT | Updated 15/07/2016 12:51 PM AEST

What Happens To Your Body On A Juice Cleanse

Grimacing mixed race woman drinking healthy drink near refrigerator
Jill Giardino via Getty Images
Grimacing mixed race woman drinking healthy drink near refrigerator

Last week I met a guy who told me he was spending $70 a day on a three-day 'juice cleanse'. While I had to admire his dedication to improving his health, I couldn't help but think about what a waste of time and money this was.

Alas, this is something I hear on an almost-weekly basis. Meanwhile, I seem to have very few conversations that start with "Oh, I just decided I would try and include more vegetables in my diet for the next few months and cut back on processed food".

It's human nature to look for a quick fix to a problem, and there's no doubt that, for the majority of us, our health and weight is a major problem. So juice cleanses or detoxes appear to offer a perfect solution; in the prescribed three to seven days you can supposedly lose weight and do a total 180 in terms of your health -- who wouldn't sign up for that?

Except, unfortunately, that's not what really happens...

Yes, you will lose weight

If it's rapid weight loss you're after, a juice cleanse will almost certainly produce the desired results. Because of the drastic reduction in kilojoule intake that occurs when you drink nothing but fruit and vegetable juice for days on end, weight loss is not exactly surprising. BUT (and it's a big but), 'weight' loss is not the same as 'fat' loss. While you will no doubt notice a decrease in the numbers on the scales, most of this will be water as your body is depleted of its carbohydrate stores and in the process loses a significant amount of fluid. What's more, the lack of protein will mean that some of the weight lost is likely to be muscle -- not the kind of weight loss you want.

You might experience some euphoric feelings of 'enhanced wellbeing'

A juice cleanse may indeed result in you looking and feeling better initially, but this is not because of any miraculous ingredients in the juices. It is simply due to the fact that you're eating far more fruit and vegetables than you normally do and you've automatically cut out highly processed foods, alcohol, saturated fat and added sugars from your diet. So the initial feelings of enhanced wellbeing are hardly miraculous.

Plus, you'll no doubt be feeling just a little bit smug as you sip on your matcha green tea and kale smoothie while everyone else poisons themselves with carbohydrates and protein. And smugness has been clinically proven to give rise to feelings of euphoria.*

But beware....

Your body will fight back

As with any extreme change, your body will sense it's under threat and will fight back. After the initial day or two, you'll most likely start experiencing extreme tiredness and hunger. This is your body trying to protect you against the famine it perceives you've been hit by, conserving its dwindling energy supplies and attempting to force you to find food.

'Hanger' is inevitable

When we restrict calories, particularly carbohydrates, our blood-sugar levels plummet, causing headaches, nausea and lethargy and leaving us grumpy and irritable. Combine this with very little fat and protein (which help to fill us up and keep us feeling satisfied), and you've got a recipe for some serious 'hanger'. Best not plan any social engagements... and warn everyone at the office.

You will probably get constipated

While fruit and vegetables naturally contain a lot of fibre, much of this is removed in the juicing process. Fibre not only helps us to feel full, it also keeps our digestive system on track, which means that there's a high chance you're going to be feeling at least a little backed up.

And prepare for the rebound

Yes, you'll probably be amazed at how quickly you lost weight during your juice cleanse. But you'll be even more amazed at how quickly you regain it when you go back to your normal diet (or any diet which involves eating actual food). Even more so, after the common post-cleanse, head-first dive into the ice-cream freezer at 7/11.

Ultimately, it's our extremism and all-or-nothing attitudes that are the real problem -- not the absence of juices in our lives. Juice cleanses just perpetuate this extremism and actually do nothing to solve our problem. We need to accept that quick fixes just don't work in the long term and focus instead on making sustainable changes that we can actually stick to. It might not be glamorous, but guess what? It actually works.

And as for the guy on the juice cleanse, I later learned that he had gone out for a huge plate of ribs before starting the 'cleanse' and had celebrated its completion with a large steak and fries. I don't think it takes a dietitian to figure out that the benefits of this three-day program would have equated to approximately zero.

*This has not in fact been scientifically proven but anecdotally I think it stands up pretty well.