A food diary is a simple record of what you eat and drink, how much, and when. Keeping one for even a week or two can show patterns you’d never notice otherwise, such as how much you snack in the evening, how often you skip vegetables, or which foods seem to trigger digestive symptoms. To keep one, write down everything as soon as you eat it, including drinks, sauces and snacks, with a rough portion size and the time. Add notes about hunger, mood or symptoms if they’re relevant to your goal. A notebook works as well as an app; what matters is being consistent and honest.
Why keep a food diary?
A food diary can help you:
- Manage your weight. Tracking what you eat makes portions, snacks and drinks visible.
- Work out food triggers. The NHS notes that you may be asked to keep a food and symptoms diary to help work out what may be triggering a food intolerance.
- Prepare for a dietitian appointment. A few days of records give a dietitian a clear picture of your usual eating. Our guide to the difference between a dietitian and a nutritionist explains who to see.
- Understand blood sugar if you have diabetes, by recording meals alongside glucose readings, as your diabetes team advises.
- Improve your diet. Seeing how often you eat vegetables, fruit, fish or whole grains is a good starting point for change.
- Spot links with energy, sleep and mood. Our guides to food and mood and diet and energy explain what to look for.
Does it help with weight loss?
Self-monitoring is one of the most consistent habits linked with weight loss. A review of 22 studies of self-monitoring, 15 of them focused on diet, consistently found a significant link between self-monitoring and weight loss, though the authors noted the evidence was weak because of how the studies were designed. In a large US weight loss trial, keeping diet records was among the behaviors that explained most of the difference in how much weight people lost; participants kept food records on almost 4 days a week on average.
A food diary doesn’t cause weight loss on its own. It works because it makes you more aware of what you eat, which makes it easier to change.
What to record
| What | Why | Example |
|---|---|---|
| Time | Shows meal patterns and long gaps | 7:30 am |
| Food and drink | The main record | Porridge with milk and banana; coffee with milk |
| Amount | Calories and nutrients depend on portions | 40 g oats, 200 ml milk, 1 small banana |
| Where and with whom | Reveals habits | At my desk, alone |
| Hunger before and after (1 to 10) | Helps you notice eating when not hungry | Before 6, after 3 |
| Mood or feelings | Links emotions and eating | Rushed, a bit stressed |
| Symptoms, if relevant | Finds triggers | Bloating 2 hours later |
You don’t need every column. If your goal is to eat more vegetables, simply tick off portions. If it’s to find a food trigger, food, time and symptoms matter most.
Paper or app?
Paper or notes on your phone:
- Simple, flexible and private.
- Good for recording feelings, hunger and symptoms.
- No calorie totals, unless you add them yourself.
Tracking apps:
- Calculate calories, macros and some nutrients from large food databases.
- Can scan barcodes, which saves time.
- Database entries are sometimes wrong, so check the ones you use most against labels or USDA FoodData Central.
- Can encourage an unhealthy focus on numbers for some people.
If you follow keto, our guide on how to track macros on keto explains what to log.
How to keep a food diary: step by step
- Decide why you’re keeping it. Your goal decides what to record.
- Choose a format you’ll actually carry with you.
- Write it down straight away. Memory is unreliable, and small snacks are the first to be forgotten.
- Include everything: drinks, sauces, cooking oil, bites while cooking, and alcohol.
- Estimate portions using household measures, packet weights or your hand: a fist for carbs, a palm for protein, a thumb for fats.
- Keep going for at least 3 days, including a weekend day, as weekends are often different. One to 2 weeks gives a clearer picture.
- Review it at the end of each week, ideally with a fresh eye.
What to look for when you review it
- Meal timing: long gaps followed by large meals or evening snacking.
- Vegetables and fruit: how many portions a day.
- Drinks: sugary drinks, juices, alcohol, and specialty coffees, which can add many calories.
- Protein and fiber at each meal, which keep you full. Our guide to building a balanced meal shows what to aim for.
- Triggers: eating when bored, tired, stressed or in front of a screen. Our guide to mindful eating can help.
- Symptoms: whether they follow particular foods, often within a few hours.
Choose one or two changes at a time, rather than overhauling everything at once.
Using a food and symptom diary
If you have bloating, stomach pain, diarrhea, headaches or skin symptoms that you think are linked to food, a food and symptom diary is a useful first step. Record what you eat, when, and when symptoms appear, along with how severe they are, stress levels and, for women, where you are in your menstrual cycle.
Don’t cut out whole food groups based on your diary alone. See your doctor first, as symptoms like these can have many causes, including coeliac disease, which needs testing while you’re still eating gluten. If you suspect a food allergy, with symptoms such as swelling, hives or breathing difficulty, seek medical advice rather than testing foods yourself.
Tips for accuracy
- Weigh foods for a few days to learn what your usual portions look like.
- Log oils and spreads. A tablespoon of oil adds about 120 calories.
- Note brands for packaged foods.
- Don’t change your eating because you’re recording it, at least at first, or the diary won’t show your real habits.
- Be kind to yourself. The diary is for information, not judgment.
When a food diary isn’t a good idea
Food tracking isn’t helpful for everyone. If you have, or have had, an eating disorder, or you find that tracking makes you anxious, guilty or obsessive about food, stop and talk to your doctor or a specialist dietitian. An eating disorder is serious but treatable, and if you need someone to talk to now, findahelpline.com lists free helplines in many countries.
Common questions
How long should I keep a food diary?
At least 3 days for a snapshot, or 1 to 2 weeks to see patterns. Some people use one long term to stay on track; others only when they want to make a change.
Do I need to count calories in my food diary?
No. Many people find it more useful to record foods, portions, hunger and mood. Our guide on how many calories you need explains calorie targets if you want to use them.
Should I record drinks?
Yes. Drinks, including alcohol, milky coffees, juices and smoothies, can add a lot of calories and sugar.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
