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What is the scientific validity of fasting?

What is the scientific validity of fasting?

The Effect of Fasting upon Human Health


Muslims all over the world observe fasting in the ninth month of the lunar calendar. It is forbidden for Muslims to eat and drink from dawn (that is, approximately one and a half hours before sun-rise) until sunset. But from sunset (iftar) until dawn (sahur), they can eat and drink whatever they want.

Fasting becomes obligatory for every healthy male who has reached the age of 15 or who has reached puberty and for every healthy female who has reached the age of 12 or who has reached puberty. As is stated in the following verse of the Qur’an, fasting is not mandatory for those who are ill or traveling:

“…But if any of you is ill, or on a journey, the prescribed number should be made up from days later…” [al-Baqarah 2:184].

Because the lunar calendar is eleven days shorter than the solar calendar year, fasting in the month of Ramadan is observed during different months of the Gregorian year. Therefore, Ramadan begins eleven days earlier each year according to the Gregorian calendar.

The fasting hours in the day change in different regions around the world and during different seasons of the year, and therefore the hardship or ease of the fast constantly changes. Sometimes the fast can last for 12 hours and sometimes for 19 hours. Thus, the number of meals may vary from sunset till dawn during different seasons in different countries.

The effects of fasting upon the human body have long been subjected to scientific research. While some studies argue that fasting has certain negative effects, many others have stated that it does not have any detrimental effects upon the organism, as long as it consists only of a change in the eating hours and the daily intake of calories does not change.

The Study

In the research conducted at the Dakar Medical School thirteen volunteers, two of whom were pregnant women, were taken as the experimental group. The main objective was to analyze the effect of fasting upon the human organism. Another object of the same experiment was a 27-year-old woman who was not fasting. Through these studies the effects of fasting upon weight, temperature, pulse, blood pressure of the body, the absorption activities of the cells, and the liquid equilibrium of the organism were analyzed. Blood and urine analyses of the participants were also carried out.


Three of the thirteen participants were women. One of them was 17, another was 27, and the other was 40. The youngest of the male participants was 22 and the oldest was 33. All participants were chosen from middle class and had an intake of 2,500 to 3,000 calories per day. What is more, all of them were healthy people with no known organic or infectious disease.

During the week before Ramadan, the normal values of the participants were recorded in order to compare them later with the values of the observers of fasting during Ramadan. Pre-Ramadan analyses were done before breakfast and during-Ramadan analyses were done after drinking some water, that is, just after breaking the fast with some water (iftar). The analyses were carried out on the first, the tenth, and the last day of Ramadan and once again 30 days after Ramadan.

• Results


Weight Loss or Gain: 

No significant change in the weight of those who were fasting was observed. Except for two volunteers, the decrease in the weight of those fasting was 2.8 kg at most.

The increase in the weight of the pregnant woman was 1.6 kg. Post- Ramadan data show that half of the volunteers regained the weight lost during the month of fasting.

2. Circulatory system: No significant effect of fasting upon pulse or temperature was observed. The hemoglobin rate of the blood was normal. This finding means that the one-month fasting was not a long enough period to cause any degradation in the hemoglobin. In general, no significant change in the blood pressure of the volunteers was evident.

3. Cellular respiration: No significant change in the cellular respiration rate was recorded during Ramadan.

4. The blood sugar balance: The blood sugar rate of the fasters significantly decreased. The decrease rate was 70 mg, which is the lowest rate for the human organism. The rates observed were no higher than 104 mg for any participants.

5. Sugar consumption in the blood: Four of the people fasting, one of whom was a woman, took part in the experiments carried out first before Ramadan and once again on the last day of Ramadan to find out the effect of fasting upon the sugar consumption rate. Analyses demonstrated that there was no significant difference between the glucose rates of fasters and non-fasters. Blood compounds were observed to be stable between the upper and lower normal levels. Moreover, the liver was found to be functioning well.

6. Fluid balance of the body: Most of the people fasting were observed to have a normal fluid balance in their body. Interestingly, some of the people fasting were able to achieve an intake of 2.4 lt. of fluid in twenty-four hours, which is slightly more than what the body requires. Urine discharge (micturation) was normal during the 24-hour period.

General Conclusion:

The medical experiments summarized above show clearly that fasting has no negative effects upon the body. Although some changes in the blood sugar values were observed, these were not above physiologically normal levels. However, it should be made clear that the abovementioned experiments were carried out on healthy participants. Therefore, the results cannot be extended to those who are sick or handicapped.

Some Comments

This scientific study conducted at Dakar Medical School has established that fasting is not harmful to the human body. There are many other scientific studies verifying the fact that fasting is even beneficial to the body. Some of its benefits are as follows:

a) The digestive system of the person fasting is able to take a complete rest. The digestive system is an organic mechanism that begins to function with the intake of the first substance that a newborn takes and it continues until the time of death. Therefore, abstaining from food for a few hours is a widely used natural method of providing relief for this system. This method is used before serious operations, as it is recommended for the patient to have an empty stomach before undergoing anesthesia.

b) It is a well-known scientific fact that eating little is more beneficial than eating a lot. That is, so long as the organism attains enough nutrients it is better to eat only at definite hours of the day and to avoid filling the stomach with non-nutritious junk food throughout the day. Actually, fasting brings about this important benefit to the body. The person fasting is advised to eat little, even when breaking the fast.

This is a sunnah, or general practice, of the Prophet, and Allah the Almighty says in the Qur’an:

“Whatever the Messenger gives you accept it willingly and whatever he brings you fulfill it, and whatever he forbids you, refrain from it” [al- Hashr 59:7].

c) It is a well-known fact that over-eating is harmful to the body. Over-eating is among the causes of some common ailments such as heart disease, high blood pressure, and diabetes. Therefore, it is an important curative method to relieve the stomach of one with unhealthy eating habits for one-twelfth of his life. Scientific studies have verified that the ailments mentioned above tend to be less common in regions where fasting is observed as an obligatory practice than in other regions in the world.

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