Drained and off your food in hot weather? What can I do?

Feeling drained, low on energy and off your food in hot weather usually comes from sweating a lot without drinking enough, and from long stretches in the sun or in hot, stuffy places. What you can do: drink regularly through the day and aim for pale yellow urine, stay in the shade especially between 11 a.m. and 3 p.m., eat small meals that are freshly cooked, and take breaks somewhere cool. If you feel faint, pass out, become confused, or feel hot but are not sweating, move somewhere cool and get help fast by calling 1669.

Thailand is hot most of the year, and March to May is hotter still. A few minutes' walk from the car park to the office can leave you soaked, outdoor work goes on all day, and a stuffy bedroom can leave you unrefreshed in the morning. This article covers why heat leaves you drained and without appetite, how to drink, eat and plan your day, and which kinds of heat are dangerous, using information from the UK's NHS and the US NIA and CDC.

Why does hot weather leave me drained and off my food?

In hot weather your body cools itself by sweating. If you lose a lot of sweat and do not drink enough to keep up, your body starts to run short of water and you tire easily. Many people also find they do not feel like eating on very hot days.

Sweating a lot, drinking too little

The NHS notes that you may need to drink more fluids than usual in a hot environment or when you are physically active for long periods. People who sit in air conditioning all day and then step out into the midday sun, or who avoid drinking so they do not need the toilet, often drink less than their body needs.

Long hours in the sun or the heat

Construction work, selling at a street stall, delivering by motorbike, or exercising outdoors at midday all heat the body up steadily. The NHS advises avoiding exercise or activity that makes you hotter during hot weather.

Drinks that leave you short of water

The NHS advises avoiding alcohol, caffeine and hot drinks during hot weather, and the NIA also advises avoiding alcohol and caffeinated drinks. An ice-cold beer after work on a hot day is not the drink to reach for.

Sleeping in a hot room

A hot, sticky night makes it hard to sleep comfortably, so daytime tiredness can come partly from poor sleep. The NHS suggests closing windows and curtains during the day and opening them at night when it is cooler outside.

Signs your body is getting too hot

The NIA says that when your body starts struggling to keep itself cool, you might feel thirsty, dizzy, weak, uncoordinated and sick, sweat a lot, and have cold, clammy skin; some people have a rapid pulse. If you feel drained and off your food along with any of these, stop, rest somewhere cool and drink straight away (see the last section).

How much should I drink in hot weather, and what?

How much, and how often

The CDC suggests carrying a water bottle and drinking and refilling it throughout the day. Keeping one in the car, your bag or on your desk makes it easy to sip without waiting until you feel thirsty.

Check your urine colour

The NHS suggests aiming to drink enough during the day that your urine is a clear pale yellow colour. You can check this every day without counting glasses.

Go easy on sugary drinks

The NIA lists water, fruit or vegetable juices, and drinks that contain electrolytes as liquids to drink in hot weather. The CDC advises limiting drinks high in sugar or sodium, so very sweet iced tea, soft drinks and energy drinks are not the best choice for quenching thirst.

It's too hot to eat. How should I eat?

When you cannot face food, you do not need to force down a big meal, but do eat something at regular intervals and take care with food hygiene. The US CDC advises never leaving perishable food out for more than 2 hours, or more than 1 hour when it is above 32°C (90°F).

Small, cool meals

The NHS suggests cold food and regular cold drinks in hot weather. Ideas that work in a Thai kitchen:

• chilled cut fruit such as watermelon, pineapple, papaya or guava as an afternoon snack
• rice with milder dishes such as steamed egg, steamed fish or stir-fried vegetables, instead of fried food or very rich, spicy curries
• a clear soup with tofu and minced pork, or a vegetable stew left to cool a little before eating, for both fluid and vegetables
• chilled milk or yoghurt on days when you do not feel like rice at all

Store and reheat food properly

The CDC's four steps to food safety (clean, separate, cook and chill) matter even more in the hot season:

• wash your hands before, during and after preparing food and before eating
• keep raw meat, poultry and seafood apart from food that will not be cooked
• cook food thoroughly, especially meat, poultry, eggs and seafood, and reheat leftovers thoroughly
• refrigerate cooked leftovers and cut fruit within 2 hours, or within 1 hour when it is above 32°C (90°F), such as in a hot car

So take extra care in the hot season with a boxed lunch bought in the morning and left in the car all day, or dishes left out on the table from lunch until dinner. Wash fruit well before cutting it to chill.

How should I plan work and time outdoors when it's hot?

Avoid the hottest part of the day

The NHS advises staying in the shade, especially between 11 a.m. and 3 p.m. The CDC suggests doing outdoor activities during the coolest parts of the day or in the evening, if possible. A run in the park at 6 a.m. or a walk after sunset suits better than midday.

Dress to stay cool

• Wear light-coloured, loose clothes that let air through.
• If you must be in the sun, wear a hat and stay in the shade as much as you can.

Take regular breaks somewhere cool

The CDC suggests using air conditioning or finding a place that has it on hot days. If you work outdoors, stop for shade and water regularly rather than waiting until you are exhausted. At home, the NHS suggests closing windows, curtains and blinds during the day and opening them at night when it is cooler outside, and says electric fans can help if the temperature is below 35 degrees. A cool shower, or putting cool water on your skin or clothes, also helps you cool down.

Which kinds of heat are dangerous, and when should I get help?

Most heat-related tiredness gets better with rest somewhere cool and enough to drink. But the signs below need action straight away.

Warning signs and what to do now

The NIA advises that when your body is getting too hot, you rest somewhere cool and drink plenty, and get medical care if you do not feel better soon.

Signs that need medical help right away

The NIA says to get medical help right away for any of the signs below, and to move straight away somewhere cooler, such as into the shade or indoors, and lower body temperature with cool clothes, a cool bath or shower, and fans:

• fainting
• confusion or acting strangely
• not sweating even when it is hot, with dry, flushed skin
• a strong, rapid pulse, or a slow, weak pulse

In Thailand, call 1669 or go to the nearest hospital.

People who need extra care

The NHS lists groups more at risk from heat: older people, especially those aged 65 and over; children aged 5 and under; people who are pregnant; people with serious long-term health problems; people who live alone; people on multiple medicines; and people who work outside or do manual work. The CDC suggests checking on family, friends and neighbours, especially those who live alone. If your parents are at home alone on a very hot day, call to ask whether they have had enough to drink and whether their room is too hot. The NIA notes that some medicines can make it harder for the body to cool itself, so if you take regular medicines, ask a doctor or pharmacist whether you need to take extra care in hot weather, and do not stop them on your own.

If you still feel drained or off your food for several weeks after the weather has cooled, and you do not know why, see a doctor.