During fasting hours when no food or drink is consumed, the body uses its stores of carbohydrate (stored in the liver and muscles) and fat to provide energy once all the calories from the foods consumed during the night have been used up. The body cannot store water and so the kidneys conserve as much water as possible by reducing the amount lost in urine. However, the body cannot avoid losing some water when you go to the toilet, through your skin , when you breathe and when you sweat if it is warm.
Depending on the weather and the length of the fast, most people who fast during Ramadan will experience mild dehydration, which may cause headaches, tiredness and difficulty concentrating. However, studies have suggested that this is not harmful to health, provided that enough fluids are consumed after breaking the fast to replace those lost during the day. However, if you are unable to stand up due to dizziness, or you are disoriented, you should urgently drink regular, moderate quantities of water – ideally with sugar and salt – a sugary drink or rehydration solution. If you faint due to dehydration, your legs should be raised above your head by others, and when you awake, you should urgently rehydrate as outlined above.
For those who would normally consume caffeinated drinks such as tea and coffee during the day, the lack of caffeine during the fast may initially lead to headaches and tiredness. This may ease over the course of Ramadan as the body adjusts to going without caffeine during the day.
Once the fast is broken, the body can rehydrate and gain energy from the foods and drinks consumed. Having not eaten for a long period, you may find it helpful to eat slowly when breaking the fast and to start with plenty of fluids and low-fat, fluid-rich foods (see suggestions below).
Drinking plenty of fluids, as well as consuming fluid-rich foods, such as fruit, vegetables, yogurt, soups and stews, is very important to replace fluids lost during the day and to start the next day of fasting well hydrated. Salt stimulates thirst and so it’s a good idea to avoid consuming a lot of salty foods. The pre-dawn meal, suhoor, provides fluids and energy for the day of fasting ahead, so making healthy choices can help you to cope better with the fast.
While iftar meals are often a time for celebration, with families and friends coming together to break their fasts, it’s important not to go overboard when eating during Ramadan. Consuming a lot of deep fried, creamy and sweet foods may actually cause you to gain weight during Ramadan. Ramadan can be a good time to make changes to improve the balance of your diet that you can sustain in the longer term.
The changes to eating habits and lack of fluids during the day may cause constipation for some people. When you can eat and drink, consuming plenty of high fibre foods, such as wholegrains, high fibre cereals, bran, fruit and vegetables, beans, lentils, dried fruit and nuts alongside plenty of fluids may help to ease constipation as well as doing some light physical activity, such as going for a walk after iftar.