How to keep a food diary for IBS, with a simple template

What to write down

Clinicians ask for the same few things. NIDDK describes a diary of "the foods and drinks you consume and when your gas symptoms occur" (NIDDK), and the NHS gives the same advice for IBS (NHS). The diary that Monash University uses for its low-FODMAP program adds symptom type, severity, bowel habit, and stress (Monash).

Here's a simple daily template built from those fields:

A few notes that make it easier to read later:

• Write the time. Food intolerance symptoms usually arrive "a few hours after eating" (NHS), so the gap between the meal and the symptom matters more than which meal came last.
• Use a small scale for strength. A 0–3 score is enough to compare days. Precision doesn't help much here.
• For bowel movements, the Bristol Stool Form Scale is the shared language doctors use, and NICE suggests it for describing stool form (NICE).
• Note medicines and supplements, including ones you take now and then. Doctors ask about them, and some affect the gut.
• Skip calories. You're looking for timing and patterns, and counting calories adds work without helping.

How long to keep it

Longer than you'd like, and for as long as you're making changes. The British Dietetic Association puts it simply: "Keep a food and symptom diary whilst you are making changes" (BDA). IFFGD, the US foundation for gut disorders, suggests a daily symptom diary for 2 to 4 weeks (IFFGD). We couldn't find a guideline that promises a trigger in a set number of days, so be wary of anyone who does.

Start with a baseline: a week or two of your normal eating. That's our suggested minimum rather than a guideline number, and longer is better if you can manage it. Then the diary keeps running while you test one change.

Change one thing at a time

This is the part that turns a diary into an answer. The BDA says to "make one change at a time so that you can see what has helped" (BDA), and Monash reintroduces foods "one at a time, so you get clear results" (Monash).

If you cut dairy, wheat, and coffee in the same week and feel better, you've learned that something in that pile matters. You haven't learned which one.

It also protects you from a common trap. When people who report a reaction to a food are re-tested with it, the ACG notes that "only 2%–3% develop recurrent symptoms" (ACG 2021). Plenty of foods get blamed for a bad day that had other causes. Testing one at a time is how you find out, and here's how to tell whether a change is working.

If you try low-FODMAP

Low-FODMAP is one of the diets IBS guidelines cover in detail, and it has a clear shape. Monash runs it in three steps:

1. Swap high-FODMAP foods for low-FODMAP ones for 2 to 6 weeks. The ACG agrees that responders can be identified in 2 to 6 weeks.
2. Reintroduce one FODMAP group at a time, eating a food rich in that group for 3 days, then taking a 2–3 day break, or until symptoms settle, before the next test. Monash says the reintroduction step takes most people about 6 to 8 weeks (Monash).
3. Personalise: keep avoiding only the foods that triggered you, and bring everything else back.

It doesn't work for everyone. Monash says about three quarters of people with IBS improve on it. And it isn't meant to be forever: step 3 exists to loosen the diet, because over-restricting can cut nutrients you need. NICE recommends advice from a professional with expertise in diet, and the British Society of Gastroenterology says a trained dietitian should supervise it (BSG 2021).

Before you cut out gluten

If there's any chance of celiac disease, get tested before you cut gluten. The blood test only works while you're still eating it: NICE advises gluten in more than one meal every day for at least 6 weeks before testing (NICE NG20). Going gluten-free first can make the result wrong. The food sensitivity guide covers the tests that do help, and when.

Start today

Print a page

The printable food and symptom journal gives each day one page, one line per entry: the time, the kind, and what happened in your words. A two-week try sheet comes with it, so the baseline, the one change, and the look-back sit on one page.

Or ask your AI assistant to set it up

If you already use an AI assistant, this prompt turns the method above into a plan you can follow. It works in any capable assistant. Check its privacy practices before you share health details.

Help me keep a food and symptom diary for my gut symptoms and test one change at a time. Help me with the method only. Don't diagnose me or suggest medicines or supplements. If I mention blood in my stool, black or tarry stools, weight loss I can't explain, diarrhea that wakes me at night, or symptoms that are new or getting worse, tell me to see a doctor first.

1. Ask what's bothering me, and write it as one question in my words, like "What's making me bloated after lunch?"
2. Give me a daily format with one line per entry: the time, the kind (meal, drink, symptom with a 0 to 3 strength, bowel movement by Bristol type, medicine, stress, sleep), and what happened in my words. No calories.
3. Pick one daily check-in for my question, answered none, a little, or a lot, at about the same time each day.
4. Plan one to two weeks of my usual eating as a baseline before any change.
5. Help me choose one change to try for about two weeks, and the date I'll look back. One change at a time. Don't suggest cutting several foods at once, going gluten-free before I've been tested for celiac disease, or starting low-FODMAP without a dietitian.
6. Give me three questions to ask of my notes each week, such as: What did I eat in the few hours before my worst afternoons? Which days broke the pattern? What else was different on those days?
7. At the look-back, if I share my notes, compare the baseline and the try as whole stretches. Count the days with symptoms in each, quote the entries you counted, and call it: helped, no clear effect, made it worse, or needs another round. Say what my notes can't tell us.

What it looks like in Kasane

Kasane is the journal version of this method. It's on the App Store for iPhone, starting with a free week: download Kasane. Here's a fictional example, step by step: Priya, who's bloated most afternoons and a few days into a two-week try.

1. The day, written the way she'd text it

The diary is the same one described above, written in sentences: Priya writes what she ate or how she feels, and each line lands at its time with a kind attached.

2. She names the question, and one change

3. Her journal connects the dots

The finding shows up on her question's page, in counts and dates from her own entries. Her try cuts noodles and bread at lunch, so if celiac disease were possible, testing would come first.

4. She looks back

A look-back is a call on one try. It's a strong clue, and the guidelines' advice still holds: one change at a time, and a dietitian for anything bigger.

5. She takes it to the visit