The practice of fasting is most commonly associated with Ramadan, when Muslims all over the world observe a month of abstaining from food and drinks from dawn until dusk. But regardless of faith and belief, many people choose to fast because of the health benefits that it is considered to have for the body.
The Benefits of Intermittent Fasting
• It boosts the immune system. Prolonged fasting protects the body against immune system damage and regenerates immune cells, according to a study conducted by Dr. Valter Longo and his colleagues from the University of Southern California.  Long periods without food kills the old and damaged immune cells and generates new ones, therefore boosting your body’s ability to shield yourself from illnesses.
• It normalizes insulin sensitivity. Fasting is an effective way to prevent insulin resistance when your body acquires too much carbohydrates and sugar. When you fast, your insulin sensitivity goes up, thus preventing diseases such as diabetes and heart complications. 
• It reduces your hunger levels. If you have a problem with binge-eating, you may try fasting to normalize your body’s ghrelin hormone production (the hormone responsible for telling your body that it is hungry).  This makes the body more accurate in telling you when it is really hungry, lessening your hunger impulses.
• It reduces high blood pressure. Fasting also helps reduce the body’s cholesterol levels over an extended period of time, which is extremely beneficial to people with cardiovascular problems. 
• It promotes the detoxification process. When you fast, your body transitions from using glucose as a main source of energy to using fat. Any toxins stored in your body’s fats are dissolved and removed, therefore detoxifying your system. This also makes fasting an excellent tool for weight loss. 
• It slows down the aging process. The body ages faster whenever Human Growth Hormones (HGH) are in low levels. HGH is largely secreted by the body during fasting, which therefore slows down your aging process.  It has also long been established by studies that overall calorific reduction leads to extended lifespan.
• It clears the skin and whitens the eyes. It is said that most skin eruptions clear up after fasting and also makes the eyes whiten.
Who Should Avoid Fasting?
Basically anyone with general good health and without any complications should be able to fast safely, except for the following people: 
• Children. It is not advisable to let children fast because their bones and teeth are still developing, and every kind of nutrition is needed for a healthy growth.
• Pregnant and nursing women. Fasting isn’t also recommended for pregnant women as it might have negative effects on the fetus. The same goes for nursing women because their breastmilk might contain fewer nutrients.
• People with eating disorders. Those with eating disorders such as bulimia and anorexia shouldn’t fast.
• People with medical complications. Included in this list are those with liver or kidney diseases, anemia, and medication-dependent diabetes.
• People who underwent a major surgery or illness. Proper recovery is essential after a major surgery or illness, so fasting is not advised for people who recently went through these.
 Longo, V., et al. 2014. Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression http://www.cell.com/cell-stem-cell/abstract/S1934-5909(14)00151-9
 Axe, J. The Many Health Benefits of Fasting http://draxe.com/the-many-health-benefits-of-fasting/
 Kirkpatrick, K. 2015. Intermittent Fasting Has Benefits Beyond Weight Loss https://health.clevelandclinic.org/2015/10/interested-fasting-health-get-facts-first/
 Fasting and Your Health http://www.nhs.uk/Livewell/Healthyramadan/Pages/fastingandhealth.aspx
 All About Fasting: Who Can Fast? http://www.allaboutfasting.com/who-can-fast.html