A practical guide to intermittent fasting, longer fasts, IBS and knowing when fasting is NOT appropriate.

Fasting is one of those subjects that seems to swing between two extremes.

At one end, it is treated like some sort of miracle cure for everything. At the other, people hear the word fasting and immediately think starvation.

The reality is a bit more sensible than either of those.

We already fast every single day. Unless you are getting up at 3am for a sandwich, there is naturally a period between your evening meal and breakfast when you are not eating. Intermittent fasting simply extends that window.

And for some people with IBS, changing WHEN they eat can be useful alongside looking at WHAT they eat.

Research into time-restricted eating specifically for IBS is still developing, so I would not advise fasting as a magic IBS treatment. But a 2026 pilot study of 16:8 time-restricted eating reported improvements in IBS symptom severity and concluded that controlled trials are now warranted.

So, let’s look at what fasting actually means, the different ways people do it, where it may be useful – and also when it absolutely is not a good idea.

Why give your digestive system a break?

Every time you eat, your digestive system has work to do: breaking food down, moving it through the gastrointestinal tract and absorbing nutrients.

That does NOT mean digestion needs to be ‘switched off’ for your body to repair itself as our bodies are far cleverer than that, but meal timing does influence digestive and metabolic processes, and constantly grazing from morning until bedtime leaves very little space between eating occasions.

For somebody already dealing with bloating, cramps, diarrhoea, constipation or that horrible heavy, over-full feeling, creating sensible gaps between meals can sometimes feel much more comfortable.

This is one of the reasons I talk about meal timing inside The IBS Freedom Method. Food matters enormously but so can HOW you eat it, WHEN you eat it and what your digestive system is dealing with across the whole day.

Overnight fasting and your body clock

Your body has its own internal clock, your circadian rhythm which helps regulate sleep, hormones, metabolism and digestion.

If you are still eating a massive meal at 10pm and going straight to bed, you may notice the difference in your digestion and sleep. For many people, simply creating a decent overnight gap is a really sensible place to begin.

So… what are the different ways to fast?

16:8 fasting

The 16:8 is really popular. You fast for 16 hours and eat within an eight-hour window. For example, you might finish eating at 6pm and eat again at 10am the following morning.

It can suit people who are super busy and would rather have fewer, proper meals than graze all day. It also creates a longer overnight break from eating.

Personally, I have used intermittent fasting for years. Most days I try to eat around 11am and finish around 5pm. Does that happen every single day? Of course not. LIFE happens. But it gives me a regular rhythm that works well for me.

The 5:2 approach

The 5:2 diet was popularised in the UK by the late Dr Michael Mosley. The basic idea is that you eat normally for five days of the week and substantially reduce your calorie intake on two days.

For some people, this can be a manageable way of reducing overall energy intake without fasting completely. It can also change the way you think about food.

Because one thing fasting has taught me over the years is food appreciation.

When food is available to us 24/7, it is incredibly easy to eat because we are bored, because it is there, because somebody else is eating, or simply because it is ‘lunchtime’. Spend a deliberate period without food and suddenly that first proper meal becomes really, really tasty!

In fact, all forms of fasting can make us much more aware of what, when and WHY we eat – and that awareness can be incredibly useful when you are trying to build a healthier long-term relationship with food.

The occasional 24-hour water fast

A 24-hour water fast is actually more like a 36-hour period between meals if you include the night’s sleep either side.

During a longer period without food, the body gradually shifts away from relying on recently consumed energy and increasingly draws on stored energy. Fasting also affects metabolic signalling and cellular processes but you do NOT need to turn this into a biology degree to understand the basic principle.

I describe the experience as a bit like an oil change for my internal systems and I personally come out of one of these feeling sharper, clearer, more focused and just a bit more ‘zingy’.

Some people include coffee or juices during these types of fasts. Personally, if I am doing a water fast, I mean to just drink water.

This is not something everybody needs to do, and more fasting does not automatically equal more benefit. An occasional 24-hour fast might be something an appropriate person chooses to do monthly, quarterly or simply a couple of times a year.

On a personal level, I have also used this method when I have felt something coming on – a seasonal cold, for example. Rather than loading myself up with food, I prefer to give myself some space, hydrate and rest. That is my personal practice, not a claim that fasting treats or cures an infection.

7, 10 and 14-day fasting retreats

NOW we are entering VERY different territory.

Multi-day fasting is not just an extended version of skipping breakfast.

7, 10 and 14-day fasts should only ever be undertaken at an appropriate professional facility or fasting retreat, with trained and qualified people on hand to assess, supervise, guide and support you.

PLEASE DO NOT TRY THIS AT HOME.

There are genuine risks with prolonged fasting. Depending on the individual and the circumstances, these can include dehydration, electrolyte disturbances, dizziness, weakness, low blood pressure, changes in blood glucose and nutritional problems.

Medication matters too. Some medicines are affected by food intake or can become problematic when somebody is fasting. Your medical history, current health, medication, nutritional status and any history of disordered eating all need to be considered before somebody embarks on a prolonged fast.

And the end of the fast matters. After a significant period without food, reintroducing food needs to be handled appropriately too. So this is absolutely NOT a case of thinking: “Helen did seven days. I’ll give it a whirl next week.” Please don’t!

BUT… this is also where my own story gets interesting

Saying that – supervised prolonged fasting has been one of the most profound experiences I have personally had.

Every time I have fasted for a prolonged period (at a retreat or appropriate facility, obviously) I have come away having experienced some sort of epiphany, shift or incredible personal transformation.

In fact, my very first seven-day fast is part of what brought me here to YOU.

It changed the way I thought about food, my body, my health and what I wanted to do with my life. That personal experience is one of the reasons fasting remains a subject I find so fascinating.

But MY positive experience does not make prolonged fasting appropriate for everybody, which brings me neatly onto the really important bit.

Why fasting is NOT for everyone

Because we are not all starting from the same place. Intermittent fasting may be inappropriate, or may need medical advice and supervision, if you:

• are pregnant or breastfeeding
• are underweight, malnourished or at risk of nutritional deficiency
• are under 18
• have a current or previous eating disorder, or fasting triggers restrictive or obsessive behaviour around food
• have diabetes or problems controlling your blood glucose
• take medication that is affected by meal timing, food intake or changes in blood glucose
• have kidney, liver, cardiovascular or other medical conditions that could be affected by fasting
• are frail, elderly or recovering from illness, surgery or significant weight loss

And even if none of those applies to you, longer does not automatically mean better.

Your health history, medication, nutritional status, energy requirements, lifestyle and the type and duration of fasting all matter.

If you have a medical condition, take regular medication or have any reason to think fasting may not be appropriate for you, speak to your GP or appropriate healthcare professional before making a significant change to the way you eat.

But what about IBS specifically?

Research into meal timing and IBS is beginning to emerge. A 2026 pilot study followed people with IBS using a 16-hour daily fasting period and an eight-hour eating window for eight weeks. Symptoms improved on average, including in constipation, diarrhoea and mixed IBS subgroups. Sounds pretty positive.

For me, fasting is one possible tool. It sits alongside the bigger picture: what you are eating, hydration, bowel habits, stress, sleep, movement, your relationship with food, your individual triggers and what is actually happening with YOUR gut.

What you eat when you ARE eating still matters

You cannot spend 16 hours fasting and then expect six hours of ultra-processed food, very little fibre, hardly any water and three glasses of wine to magically become ‘healthy’ because you ate it inside a fasting window. Nice try…

Your eating window still needs to provide enough energy, protein, healthy fats, fibre, micronutrients and fluids for your particular needs.

This is particularly important for anybody with IBS who has already started cutting foods out because they are frightened of triggering symptoms. I am not advocating that fasting becomes another way of unnecessarily restricting an already limited diet.

A sensible place to start

If fasting is appropriate for you and you want to experiment with meal timing, you do not need to launch yourself into anything dramatic. Start by looking at your normal overnight gap.

Could you finish dinner and simply stop grazing afterwards? Could you leave breakfast a little later if you genuinely are not hungry first thing? Could you eat proper meals rather than nibbling from morning until bedtime? For some people, this is enough of a change to notice a difference.

Then pay attention to your body. Your energy. Your bowels. Your sleep. Your concentration. Your hunger. Your IBS symptoms.

If you feel dreadful, dizzy, weak, excessively hungry, unwell or it starts creating an unhealthy preoccupation with food simply stop. Fasting is a tool, not a health halo or badge of honour.

How I use fasting inside The IBS Freedom Method

Inside The IBS Freedom Method, fasting is not thrown at you as some random ‘gut health hack’. We look at it in context.

By the time we discuss fasting, you have already learned a lot about your digestive system, your food choices, your symptoms and how your own body responds.

That is the important bit for me. I want you to understand WHY you are doing something rather than blindly following the latest thing you saw somebody shouting about on Instagram.

For some people, fasting may become a useful part of their long-term routine. For others, it will not be appropriate at all. Both are completely valid outcomes.

Thinking about a longer fasting retreat?

I will also keep you posted when I run my next professionally supported fasting / detox retreat, simply subscribe to my newsletter below for updates

That is the environment in which I believe prolonged fasting belongs: properly planned, appropriately screened, supported and with qualified people available – alongside a group of people going through the experience with you.

Final thought

Fasting can be fascinating. It can teach you an enormous amount about hunger, habit, food, your body and your relationship with eating.

But it is not a cure-all, it is not appropriate for everybody, and when we move from everyday intermittent fasting into prolonged fasting, the level of caution and support needs to change with it.

If you have IBS and are constantly trying to work out WHAT to eat, WHEN to eat, what is triggering you and why your gut seems to have a mind of its bloody own, then this is exactly the sort of thing we work through inside The IBS Freedom Method.

And if you are not sure what is going on with your gut in the first place, you can book a Free Gut Health Call with me and we can have a proper look at what is happening and what your next step might be.

About Helen Jane

Helen Jane is a qualified Nutritional Therapist and IBS Coach with over 10 years of experience helping people reduce IBS, bloating, food intolerances, digestive discomfort, and low energy through practical nutrition and lifestyle changes. As founder of Your IBS Freedom, she specialises in helping people improve gut health naturally using food as medicine – without restrictive fad diets or unnecessary overwhelm, supporting clients across the UK, Europe, and the USA. Read client success stories and reviews here: Reviews

Disclaimer
This blog is for educational purposes only and is not a substitute for personalised medical advice, diagnosis, or treatment from your GP or healthcare professional.