When the body is starved of food, it starts to burn fat so that it can make energy. This can lead to weight loss. However, if you fast for too long your body will eventually start breaking down muscle protein for energy, which is unhealthy.
Dr Razeen Mahroof, an anaesthetist from Oxford, says there's a strong relationship between diet and health.
“Ramadan isn’t always thought of as being an opportunity to lose weight because the spiritual aspect is emphasised more generally than the health aspect," he says. "However, it’s a great chance to get the physical benefits as well.”
Source of energy during a fast
The changes that happen in the body during a fast depend on the length of the continuous fast. The body enters into a fasting state eight hours or so after the last meal, when the gut finishes absorbing nutrients from the food.
In the normal state, body glucose, which is stored in the liver and muscles, is the body’s main source of energy. During a fast, this store of glucose is used up first to provide energy. Later in the fast, once the glucose runs out, fat becomes the next source of energy for the body.
With a prolonged fast of many days or weeks, the body starts using protein for energy.
This is the technical description of what is commonly known as "starvation". It is clearly unhealthy and involves protein being released by the breakdown of muscle, which is why people who starve look very thin and become extremely weak.
However, you are unlikely to reach the starvation stage during Ramadan, because the fast is broken daily.
Gentle transition from glucose to fat
As the Ramadan fast only lasts from dawn till dusk, the body's energy can be replaced in the pre-dawn and dusk meals.
This provides a gentle transition from using glucose as the main source of energy, to using fat, and prevents the breakdown of muscle for protein.
Dr Mahroof says the use of fat for energy helps weight loss. It preserves the muscles and eventually reduces your cholesterol level. In addition, weight loss results in better control of diabetes and reduces blood pressure.
“A detoxification process also occurs, because any toxins stored in the body’s fat are dissolved and removed from the body,” says Dr Mahroof.
After a few days of the fast, higher levels of endorphins appear in the blood, making you more alert and giving an overall feeling of general mental wellbeing.
A balanced food and fluid intake is important between fasts. The kidneys are very efficient at maintaining the body’s water and salts, such as sodium and potassium. However, these can be lost through perspiration.
To prevent muscle breakdown, meals must contain enough energy food, such as carbohydrates and some fat.
“The way to approach your diet during fasting is similar to the way you should be eating outside Ramadan," says Dr Mahroof. "You should have a balanced diet, with the right proportion of carbs, fat and protein.”