Eating out for days and my stomach feels off. What can I do?

When you eat out for several days in a row, your stomach often feels off because oily and fried dishes, big portions, late, irregular and rushed meals, and sweet or fizzy drinks all add up, and food that has been sitting out plays a part too. You do not have to stop eating out. Cut back on the habits the UK's NHS lists as causes of bloating, such as fried and fatty food, large meals late at night, eating fast and fizzy drinks: order boiled, steamed or clear-soup dishes instead of fried ones, eat slowly, drink water instead of fizzy drinks, and choose food that is cooked and served hot. If you see blood in your poo, have a fever, or diarrhoea lasts more than 7 days, see a doctor.

Why does eating out for several days in a row upset my stomach?

One meal out rarely matters. When every meal for several days comes from a street stall, a food court or a delivery app, the same habits repeat at every meal, and your stomach notices.

Oily, fried and creamy dishes

Many popular dishes are stir-fried in plenty of oil, deep-fried, or made with coconut milk: fried chicken, crispy pork, omelette on rice, green curry. The UK's NHS lists fatty, spicy, processed and sugary foods among the things that can make you feel bloated. Having them at lunch and dinner for several days means your stomach gets them again and again.

Big portions and late dinners

Restaurant and stall portions can be large, and a late dinner after work is common. The NHS lists large meals, particularly late at night, as a cause of bloating, and suggests smaller, more frequent meals instead of large ones.

Irregular meal times and eating fast

On busy days you may skip lunch, then eat a large meal late, or eat at your desk in ten minutes. The NHS notes that you swallow air when you eat, which can cause bloating, and suggests chewing with your mouth closed. Northern Ireland's official advice site, nidirect, suggests eating slowly and stopping when you are full instead of clearing your plate.

Sweet, fizzy and caffeinated drinks

Iced sweet tea, soft drinks, coffee and an after-work beer often come with meals out. The NHS suggests cutting down on fizzy drinks, alcohol and caffeine if you feel bloated.

Food that has been sitting out

The CDC says germs grow quickly in food kept between 40°F and 140°F (about 4°C to 60°C), and advises never leaving perishable food out for more than 2 hours, or 1 hour above 90°F (about 32°C). In a hot climate, dishes that sit in trays at room temperature for a long time, or takeaway left in a bag for hours, deserve more care.

If your stomach also plays up when you are stressed, see Stress gives me diarrhoea then constipation. What can I do?

I have to eat out every day. What should I order?

You do not have to stop eating out. Change what you order and how you eat it. nidirect suggests choosing dishes that are grilled, boiled, poached, steamed or stir-fried (ask for little oil in a stir-fry) rather than battered or deep-fried, sauces that are vegetable- or tomato-based rather than creamy, and adding vegetables as a side dish if your meal does not include them.

A general guide for everyday meals: the 2:1:1 plate

For everyday meals, Thailand's food-based dietary guidelines advise eating vegetables and fruit regularly, and the Thai Department of Health suggests dividing your plate into 4 equal parts: 2 parts fresh or cooked vegetables of more than 2 kinds, 1 part rice or starch, preferably unpolished, and 1 part protein, mainly fish and lean meat. It suggests cutting down on fried food and avoiding meat with skin, choosing dishes that are steamed, made as a spicy salad (yam), baked, boiled, stewed or grilled, and having 1 small plate of fresh fruit that is not too sweet, such as papaya, dragon fruit or rose apple. When you eat out you cannot always split the plate exactly, but you can use it as a guide when ordering: add one vegetable dish, and choose a steamed or boiled dish instead of a fried one.

Small changes when you order

• Ask for less oil, or for the sauce on the side, as nidirect suggests for dressings.
• Add a plate of morning glory stir-fried with little oil, a clear vegetable soup or fresh vegetables when the main dish has none.
• If the portion is large, share it or stop when you are full. nidirect suggests having a smaller portion or sharing.
• Choose water instead of a fizzy or alcoholic drink.

Choose food that is cooked and served hot

The CDC's advice for travellers says fully cooked foods served hot are the better choice, and that raw or undercooked meat, fish, shellfish and eggs carry more risk. Wherever you buy food, pick dishes cooked to order and still steaming. Take more care with dishes that have stood at room temperature for a long time, and with raw seafood, raw pickled crab and papaya salad with raw ingredients.

What can I change in my meals on days I eat at home?

On days when you can eat at home, keep it simple. You do not need special foods. Look at how much, how fast and when you eat.

A simple home meal

• Cook by boiling, steaming, stewing or grilling, such as a clear vegetable soup, steamed fish or a steamed egg, as the Thai Department of Health suggests. If you need oil, it suggests vegetable oil, no more than 2 teaspoons per meal.
• Eat every meal. The Thai Department of Health advises not skipping any meal and keeping portions moderate instead.
• After several days of large meals out, make the portion moderate. The NHS suggests smaller meals instead of large ones.

Water and drinks

• Drink water through the day instead of fizzy or sweet drinks. Keep a water bottle at your desk so you can sip regularly.
• Cut down on soft drinks, alcohol and caffeine. Thailand's food-based dietary guidelines also advise cutting down on sweet, fatty and salty food, drinking enough clean water, and avoiding or cutting down on alcohol.

How and when you eat

• Eat slowly and stop when you feel full.
• Chew with your mouth closed, which the NHS suggests to avoid swallowing air.
• Avoid a large meal late at night, which the NHS lists as a cause of bloating.
• Move regularly. The NHS suggests regular exercise; a walk after dinner is an easy start.

How do I keep food clean when I eat out or take food home?

Look at the food, your hands and the time it has been sitting out. The CDC's four steps for food at home are clean, separate, cook and chill.

Takeaway and delivery

• In hot weather, eat takeaway soon after you get it, or put it in the fridge as soon as you get home.
• Do not leave food in the car or in a bag for hours.

Drinks

The CDC's advice for travellers says drinks from unopened, factory-sealed bottles or cans and drinks made with water that has just been boiled, such as hot tea and coffee, are the better choice, and to avoid ice unless you are reasonably sure it was made from clean water.

When should I see a doctor about an upset stomach?

The NHS says diarrhoea usually stops within 5 to 7 days and vomiting within 1 or 2 days.

Get medical advice soon if

• there is blood in your diarrhoea
• diarrhoea lasts more than 7 days, or vomiting more than 2 days
• you cannot keep fluids down
• you show signs of not having enough fluid; a pharmacist can also advise
• you have diarrhoea and a fever, which the CDC also lists as a reason to contact a healthcare provider
• you feel bloated regularly, have lost weight without trying, or see blood in your poo, as the NHS advises for bloating

Get urgent help if

• you vomit blood
• you have severe stomach pain

If your stomach is off every time you eat out, even after changing what you order, talk to a doctor to look for the reason together. If you take regular medicines, tell the doctor about them too, as some medicines can affect the stomach.