Asthma UK have produced the following information to help people fasting.
Fasting is willingly abstaining from some or all food, drink, or both, for a period of time. An absolute fast is a complete abstinence from all food and liquid for an amount of time. Other fasts may only limit particular foods or substances. Fasts may also be partial in nature, for example for a set period each day for a set length of time, such as Ramadan. Fasting may preclude sexual intercourse and other activities like smoking and drinking alcohol.