The Science Behind Intermittent Fasting
and Its Benefits
Intermittent fasting (IF) is not a new concept but has experienced a renaissance in modern times. Intermittent fasting (IF) has gained significant traction recently as a weight loss strategy and a means to improve overall health. While the concept of fasting has ancient roots, modern science has illuminated the numerous physiological benefits that can be derived from this practice
Religion and the History of Fasting
The practice of abstaining from food, known as fasting, traces back centuries. Religious tenets from Christianity, Islam, Buddhism, and Judaism have ritualized fasting. Outside of spiritual realms, fasting historically served therapeutic purposes under the belief that it could purify both body and soul.
- Lent: One of the most recognized fasting periods in Christianity is Lent, 40 days of penance, prayer, and fasting leading up to Easter Sunday. The number 40 has biblical significance, reminiscent of the 40 days Jesus spent fasting in the desert.
- Advent Fast: Preceding Christmas, this fast spans four weeks, signifying spiritual preparation to celebrate Christ’s birth.
- Fasting on Wednesdays and Fridays: Early Christians fasted on these days to commemorate the betrayal and crucifixion of Jesus. Over time, practices varied among denominations, but the significance remained.
- Ramadan: Muslims observe a month-long fast during Ramadan from dawn until sunset, commemorating the month the Quran was revealed to the Prophet Muhammad. The fast is about abstaining from food and refraining from sinful behaviors.
- Ashura: Observed by some Muslims on the 10th day of Muharram, this fast commemorates various events, including the day Noah left the Ark or Moses’ exodus from Egypt.
- Mondays and Thursdays: Some Muslims choose to fast on these days based on the traditions of the Prophet Muhammad, believing these were the days he fasted regularly.
- Yom Kippur: The Day of Atonement is the holiest day in the Jewish calendar. A strict 25-hour fast is observed, accompanied by intensive prayer and reflection on one’s deeds.
- Tisha B’Av: This day marks the destruction of Jerusalem’s First and Second Temples. A full 25-hour fast is observed.
- Minor Fasts: There are other minor fast days in the Jewish tradition, such as the 10th of Tevet or the Fast of Esther, which typically last from dawn to dusk.
- Uposatha: This observance day, occurring every lunar fortnight, is marked by increased meditation, chanting, and fasting. Some Buddhists abstain from eating after noon until sunrise the next day.
- Vassa: During this three-month monastic retreat during the rainy season, monks focus on meditation, reflection, and sometimes stricter fasting.
- Ekadashi: Observed twice a month, on the 11th day of each lunar fortnight, it’s a day of fasting where many Hindus abstain from grains.
- Navaratri: Spanning nine nights, this festival involves worshipping the goddess Durga. Many devotees fast, often consuming only fruits and dairy.
- Paryushana: The most prominent festival in Jainism involves eight or ten days of fasting, repentance, and reflection.
- Anekantavada: Some Jains fast on this day, celebrating the principle of non-absolutism.
Intermittent Fasting Options/Methods
- 16/8 Method: An 8-hour eating window is followed by a 16-hour fast, e.g., meals between 12 p.m. to 8 p.m.
- 5:2 Diet: Eat as usual for five days and limit intake to 500-600 calories on two non-consecutive days.
- Eat-Stop-Eat: Involves a 24-hour fast either once or twice a week.
- Alternate-Day Fasting: Alternate between regular eating days and fasting days. Some variations permit around 500 calories on fasting days.
- Warrior Diet: Primarily fast for 20 hours, punctuated by a 4-hour eating window in the evening.
- Random Meal Skipping: Rather than a fixed schedule, meals are skipped based on individual feelings or activities.
Benefits at Each 2-hour Interval of the Fast
- Hour 0-2: Post meal, the body is digesting and absorbing food. High insulin levels favor fat storage.
- Hour 2-4: Digestion continues, and blood sugar levels stabilize.
- Hour 4-6: The body transitions from the fed to the post-absorptive state. Insulin decreases, and energy comes from glycogen stores.
- Hour 6-8: Glycogen stores deplete, and the body increases fat oxidation.
- Hour 8-10: Fat becomes the primary energy source as glycogen is further reduced.
- Hour 10-12: The body fully enters a fasted state, significantly utilizing fat stores. Ketones begin to be produced in minimal amounts.
- Hour 12-14: Fat oxidation is in high gear, and autophagy initiates, facilitating cellular repair and cleaning.
- Hour 14-16: Ketone production increases, providing an alternative energy source that is especially beneficial for brain function.
- Hour 16-18: Autophagy continues, removing damaged cells and producing new ones. The body is deeply in a fat-burning mode.
- Hour 18-20: The benefits of autophagy become more pronounced, and there’s a notable increase in metabolic rate.
- Hour 20-22: Energy levels are maintained through ketones. Cellular repair and regeneration are at their peak.
- Hour 22-24: By this point, the body is reaping the full benefits of intermittent fasting, including improved brain health, reduced inflammation, and enhanced metabolic functions.
Intermittent fasting, with its variety of methods and proven benefits, is a compelling choice for many in pursuit of better health. As always, personal circumstances should guide one’s choices, and a consultation with a healthcare expert is paramount before embarking on such a regimen.