Juice Fast vs Juice Cleanse vs Water Fast: What's the Difference?

We collaborated with Nutritional Therapist Grace Kingswell (@gracekingswell), who designs the Presscription cleanses, on this guide to juice fasting. Fasting is everywhere right now, but it isn't really a trend. Humans have gone long stretches without a big meal for most of history; a steady supply of energy-dense food is the recent part. Below we explain what a juice fast is, how it compares with a juice cleanse and a water fast, how long people do it, and how to start and finish one well.

What is a juice fast?

A juice fast is a short period where you replace all your meals with freshly pressed juices. You keep drinking water and herbal tea, but you skip solid food. Most people do one for between one and five days, often as a reset after a busy or indulgent stretch, or as a gentle introduction to fasting.

A fast doesn't have to mean eating nothing at all. It can simply be a period of significantly lower calorie intake. That might be music to your ears if you'd like to try fasting but don't think you could do it on water alone.

The juices you choose matter. The lower the sugar, the better: by not spiking your blood sugar too high you can more closely mimic a fasted state. That's why green juices that are mostly vegetables rather than fruit are the best fit. Every Presscription cleanse is roughly 80% veg and 20% fruit, cold-pressed, made fresh to order daily, never pasteurised and delivered in glass bottles.

Juice fast vs juice cleanse vs water fast

Juice fast vs juice cleanse: in practice these are the same thing. "Juice cleanse" is the more common term in the UK and "juice fast" is used more by people coming from the fasting world, but both mean a set number of days on juice alone. Browse our juice cleanse range and you're looking at juice fasting plans.

Juice fast vs water fast: a water fast means no calories at all, just water. It's a much bigger ask, and longer water fasts are best done with professional guidance. A juice fast still provides some energy, plus vitamins, minerals and hydration, so most people find it easier to stick to and easier to fit around work and life.

Juice fast vs intermittent fasting (16:8): the most popular type of fast, and by far the easiest, is the 16:8. You fast for 16 hours and eat during an 8-hour window, for example finishing dinner by 8pm and not eating again until midday. We all fast overnight anyway, so it's mostly about skipping breakfast. You can also do it by skipping your evening meal, which may suit sleep better as you're not digesting a big meal in bed, though it's harder socially. A juice fast is different: you don't time your meals, you replace them.

What happens when you fast?

When you finish a meal you enter what's called the postprandial state. This lasts around four hours, roughly the time it takes food to leave the stomach. After that comes the post-absorptive state, when the body moves on from digesting your last meal and starts drawing on its stored energy, namely glycogen (how carbohydrates are stored) and some fat. This lasts about six more hours.

If you eat every few hours, you never really reach the point where your body has to look elsewhere for fuel. Somewhere after 14 to 16 hours of fasting or calorie restriction, a process called autophagy also picks up. Autophagy is the way our cells clear out and recycle their old, worn-out parts. It happens all the time, but it is increased by periods of fasting, so despite the scary name it's a good thing. A low-sugar juice fast is one way people try to get some of these fasting effects while still having something to drink and look forward to.

How long should a juice fast be?

• 1 day: the best place to start if you've never fasted. One day is enough to see how you feel without any big commitment.
• 3 days: the most popular length. Day one is usually the hardest; by day two or three many people say they feel lighter and more energised. Our 3 day juice cleanse is the one we recommend for most people.
• 5 days: for people who have done a juice fast before and know how their body responds. Prepare well and plan a quieter week.

We don't recommend going longer than five days without professional guidance.

What a juice fast day looks like on Presscription

Each day you get 6 juices and 2 shots, numbered so you know exactly what to drink and when. Spacing them every couple of hours keeps your energy steady:

• 9:30am – Juice 1
• 11:30am – Juice 2
• 12:30pm – Shot 1
• 1:30pm – Juice 3
• 3:30pm – Juice 4
• 4:30pm – Shot 2
• 5:30pm – Juice 5
• 7:30pm – Juice 6

Drink plenty of water and herbal tea in between. Keep your bottles in the fridge, give each one a shake before drinking, and take your time with them rather than downing them in one go.

Want to see what that looks like in practice? Our juice diet guide walks through a full day on a cleanse, bottle by bottle.

How to prepare for a juice fast

The few days before matter as much as the fast itself. Start cutting back on caffeine, alcohol, sugar and processed food two or three days ahead, and lean on vegetables, fruit, whole grains and plenty of water. This makes the first day noticeably easier. Our full guide on how to prepare for a juice cleanse walks you through it day by day.

How to break a juice fast

Don't finish your last juice and head straight for a burger. Ease back in over a day or two with light, simple foods: soups, steamed vegetables, fruit, eggs, and then gradually heavier meals. Keep up the water and go easy on alcohol and caffeine for a little longer. See our guide on what to eat after a juice cleanse for meal ideas.

Who should check with a GP first?

A juice fast isn't for everyone. Speak to your GP before starting if you:

• are pregnant or breastfeeding;
• have diabetes or any blood sugar condition;
• have a kidney condition, or take medication that is affected by diet (for example blood thinners or blood pressure medication);
• have a history of disordered eating;
• are under 18, or have any other ongoing health condition.

If you feel faint or unwell during a juice fast, stop and eat something light.

Juice fast FAQs

Is a juice fast the same as a juice cleanse?
Yes. Both mean replacing your meals with fresh juices for a set number of days. "Juice cleanse" is simply the more common name in the UK.

How long should a juice fast last?
Most people do 1, 3 or 5 days. Start with one day if you're new to it; three days is the most popular. We don't recommend going beyond five days without professional guidance.

Can you lose weight on a juice fast?
Because a juice fast is lower in calories than a normal diet, some people do see the scales move. Much of a short-term change is water, so think of a juice fast as a reset rather than a long-term weight-loss plan. Results vary from person to person.

Is a juice fast better than a water fast?
Neither is "better"; they're different. A juice fast gives you some energy, vitamins and minerals, so it's easier to stick to and fit around normal life. A water fast is far stricter and best done with professional guidance.

Can I drink coffee during a juice fast?
Ideally not. Water and caffeine-free herbal teas are best. If you rely on coffee, cut down in the days before your fast so you don't get a headache on day one.

What our customers say...

"Great delivery, yummy and made me feel amazing. 100% recommend!!" – Ayla, The Advanced Cleanse

Ready to try one? Start with our 3 Day Juice Cleanse, or see the full juice cleanse range including 1 day and celery juice options.