Dr Amtul Razzaq Carmichael, UK
In a historic address, Hazrat Musleh Mau’ud, (ra), the second Head of the worldwide Ahmadiyya Muslim Community encouraged Muslims to intermittently fast throughout the year, outside the month of Ramadan. This address inspired me to investigate the scientific concept of intermittent fasting. I wished to understand if the recommended Islamic practice of fasting throughout the year intermittently is in concordance or against the science in terms of health benefits.
The scientific concept of intermittent fasting is broadly defined as eating patterns in which food consumption is done interspersed with a long period of avoidance of any calorific food. This differs from the Islamic concept of fasting where no food or drink are allowed during the fasting period, some food is recommended at the beginning of the fasting period lasting from dawn to dusk.
I am most grateful that I had the opportunity to explore this subject with Dr. Mark Mattson, Professor of Neuroscience at Johns Hopkins University. Professor Mattson has studied the health impact of intermittent fasting for 25 years. I began by asking my introductory question.
Intermittent fasting is an umbrella term and can take various forms of controlling food intake. I asked Professor Mattson, given the differences between the Islamic practice of fasting and scientifically studied practice of intermittent fasting, can we apply the scientific evidence gleaned from intermittent fasting on the Islamic practices of fasting?
Professor Mattson said that the scientific evidence suggests that at least 12-16 hours of fasting is required for health benefits. Ideally, this would be done daily throughout the year. Depending upon where on Earth a Muslim lives, they may or may not fast for 12 or more hours during the month of Ramadan. The frequency of the fasting periods during the weeks and months of a year is also important because health benefits will only be realised over time. This is like exercise which benefits a person as long as they keep exercising regularly, but if they stop exercising their health will decline somewhat compared to when they were exercising.
I explored this idea further by asking about the health benefits of intermittent fasting that go beyond weight management.
The benefits of intermittent fasting extend much beyond weight management. There is evidence to suggest that intermittent fasting can decrease the inflammation throughout the body. Intermittent fasting improves cardiovascular function and decreases the risk factors for cardiovascular disease, such as lowering the triglycerides and LDL . 
Professor Mattson adopted it himself about 20 years ago and believes that “intermittent fasting could be part of a healthy lifestyle.” He explained that intermittent fasting improves insulin sensitivity and protects against diabetes. In published studies with human participants, it is shown that intermittent fasting can reverse diabetes in some individuals. For this reason, overweight individuals are more likely to benefit from the eating pattern of intermittent fasting.
One of the modern-day diseases, called Metabolic syndrome, is a combination of insulin resistance, hypertension, and abdominal obesity. Our body needs insulin to metabolise glucose. With insulin resistance, despite high levels of insulin, the level of glucose in the blood remains high. This is a major risk factor for heart disease. An increasing amount of evidence indicates that intermittent fasting can improve many of the key features of the metabolic syndrome by decreasing fasting glucose, fasting insulin, and insulin resistance. 
Given the benefits of the eating pattern of intermittent fasting, I asked Professor Mattson in his experience, what the optimum number of days are per month that we should observe intermittent fasting to gain health benefits.
Professor Mattson explained that intermittent fasting is an eating pattern and not a diet. Humans, through various phases of evolutionary progress, especially before agricultural revolution, had to go through extended periods of food deprivation. Here in response to his question on if I believed in evolution, I briefly mentioned the Islamic concept of evolution that we believe in (evolution within species) necessary for human development and progress.
Professor Mattson continued by explaining that earlier humans had a greater chance of survival if they could function well in a state of food deprivation. The evidence suggests that a 16-hour period of food deprivation or fasting is likely to benefit humans, but 18 hours is even better. Humans need to work for their food and Professor Mattson said that there is evidence to suggest that fasting enables the human mind to think better and more clearly.
This is an interesting concept; glucose is the main source of energy for the body cells. When a period of fasting starts, the stored glucose in the liver is used within the first 12 hours. When these glucose stores are depleted, stored fatty acids are released into the bloodstream from fat cells to provide energy. These fatty acids are turned into ketone bodies in the body.  This metabolic switch in the source of fuel is accompanied by cellular and molecular adaptations of neural networks in the brain. This enhances their functional capacity and bolster their resistance to stress, injury and disease . 
My research on intermittent fasting revealed that the heart and brain cells are individual lifelong units, these cannot be replaced, therefore getting these to function optimally contributes to healthy living and longevity. During fasting, when the brain must rely on ketone bodies for functioning, fewer harmful waste products are generated, and this can help to improve the brain function.
Professor Mattson suggested that intermittent fasting can be practised as a way of an eating pattern throughout the year, but health benefits can be observed even after intermittent fasting for one day per week; even one day is better than nothing. Animal studies showed that intermittent fasting practice was beneficial even when animals were fed a diet rich in fat and protein during the non-fasting hours.
Given the physical and mental health benefits of an eating pattern of food deprivation for a period, during a 24-hour day, at what age can we start observing this eating behaviour? I asked if there is any age limit for the practice of intermittent fasting and whether intermittent fasting contraindicated in certain medical conditions.
Professor Mattson expressed the opinion that there is no age limit for intermittent fasting; he gave the example of human studies where obese children may find that it is beneficial to undertake intermittent fasting to lose weight and attain other health benefits. Professor Mattson also suggested that intermittent fasting can be done by otherwise healthy elderly people in a cautious way.
I asked Professor Mattson if he has any tips to help adhere to the practice of intermittent fasting long-term. He explained that the human body needs to adapt to this pattern of eating behaviour. A period of one month is required to help body to adapt, train the body to the new eating pattern. This will enable to make intermittent fasting a part of life and mainstream working.
Given the scientific progress in this field and increasing public acceptance, I asked Professor Mattson, what does he see for the future of intermittent fasting; and based on his vast knowledge, does he have a message about this for our readers?
I was really inspired by the thoughtful answer of Professor Mattson, who said that human development thrives during the period of fasting. Professor Mattson, who is considered a leader in the field of cellular and molecular mechanisms underlying neuronal plasticity, explained that the power of creativity and imagination evolved and enhanced in the situations of food scarcity. Periods of fasting in the early ages enabled humans to make tools to hunt and process food. In terms of future research, Professor Mattson explained that the evidence regarding the benefits of intermittent fasting is largely from Caucasian western individuals. Data from populations with high diabetes incidence, such as Southeast Asians is not widely available. This may be an area of future research.
Research regarding the religious fasting practices of Ramadan are not randomised studies and hence do not meet the criteria of scientific robustness. Islamic fast during the month of Ramadan takes place at different times of the years and people with varying climatic conditions observe the fast in the same prescribed manner. So, the physiological challenge that fasting during the month of Ramadan poses to the human body are neither universal nor standardised. As for ethical reasons, randomisation to fast or not to fast is not possible. Therefore, some innovative trial design may be required to harness robust evidence from the religious fasting practices.
In summary, to attain, prepare, cook, and consume food is the most basic, instinctive, and vital human activity. Humans have always known that food is essential for life and with scientific progress, we have learned that amount, composition, proportions, and pattern of food consumption are essential for health. Modern living has contributed to many ailments that result from excessive food consumption such as obesity, type 2 diabetes, heart conditions and some cancers. Intermittent fasting helps the human body by making metabolic pathways that are efficient and promote survival. A period of food deprivation can help cells to eliminate harmful waste products and kickstart new cellular pathways for ultimately healthier cells. My search for scientific evidence demonstrates the benefits of this fasting eating pattern. Furthermore, I found Islamic teachings were well aligned and in concordance with current scientific concepts, though more evidence is needed. This short article provides an insight into the numerous health benefits of intermittent fasting practises.
- de Cabo, R., Mattson, M.P., 2019. Effects of Intermittent Fasting on Health, Aging, and Disease. N. Engl. J. Med. 381, 2541–2551.
- Anton, S.D., Moehl, K., Donahoo, W.T., Marosi, K., Lee, S., Mainous, A.G., Leeuwenburgh, C., Mattson, M.P., 2018. Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting. Obes. Silver Spring Md 26, 254–268. https://doi.org/10.1002/oby.22065
- Mattson, M.P., 2019. An Evolutionary Perspective on Why Food Overconsumption Impairs Cognition. Trends Cogn. Sci. 23, 200–212. https://doi.org/10.1016/j.tics.2019.01.003
- Mattson, M.P., Moehl, K., Ghena, N., Schmaedick, M., Cheng, A., 2018. Intermittent metabolic switching, neuroplasticity and brain health. Nat. Rev. Neurosci. 19, 80–80. https://doi.org/10.1038/nrn.2017.156