Why do people fast? Why is intermittent fasting so popular? Here’s a bit of history, mystery, and wellness rationale on the human practice of fasting.
Intermittent fasting involves alternating cycles of fasting and eating. Rather than dictating what to eat, it instead informs when to eat. Aside from religious traditions of fasting as an expression of sanctity and sacrifice, studies also suggest that fasting may support weight loss, protect against disease, improve metabolic health, and perhaps help prolong life.1
Fasting Throughout Time and Religion
Fasting for religious and spiritual reasons has been a part of human custom for thousands of years. It is mentioned in the Old Testament and New Testament of the Bible, the Qur’an, the Mahabharata, and the Upanishads. Fasting is particularly important for Christians during Lent and for Muslims during the holy month of Ramadan. In many religions, fasting is a way to cultivate mental discipline. When combined with prayer and meditation, it is used to exercise control of the physical body.2
Fasting for Buddhists is a form of asceticism, which is a life characterized by abstinence from worldly pleasures.3 Theravada monks and nuns, who follow the Vinaya monastic rules, do not eat each day after their noon meal. However, they consider this to be a disciplined regime aiding in meditation, not just a fast.4
Nyungne, which translates to “abiding by the fast,” is practiced by Tibetan monks and can be effective in the healing of illnesses, the nurturing of compassion, and the purification of negative karma.5 While partaking in Nyungne, a person follows the eight precepts on the first day and refrains from water and food on the second day.
Fasting is practiced in several Christian denominations. Lent, for example, is a fast that is observed in Anglicanism. It is a 40-day partial fast to commemorate the fast of Christ during his temptation in the desert.
Biblical accounts of fasting include:
- Moses fasted for 40 days and 40 nights while on the mountain with God. (Exodus 34:28)
- The prophet Joel called for a fast to avert the judgment of God.
- Jesus said: “But this kind does not go out except by prayer and fasting.” (Matthew 17:21)
- Isaiah 58:3-7 describes fasting as a means to abstain from hunger, thirst, or any lustful needs we may yearn for.
- Jesus told his followers to fast in private and not to gain favor from men. (Matthew 6:16-Matthew 6:18)
Fasting is integral to the Hindu religion, but many individuals observe different kinds of fasts based on personal beliefs and local customs. Some Hindus fast on certain days of the week, such as Ekadasi or Purnima.6 Thursdays, however, is a very common day to fast among the Hindus of northern India.
Methods of fasting vary between Hindus, but if followed strictly, no food nor water is consumed from sunset until 48 minutes after the following day’s sunrise.7 Fasting may also require avoidance of certain types of food or limiting oneself to 1 meal a day.
Fasting is the most important practice during the month of Ramadan, from fajr (dawn) to maghrib (sunset). During this time, Muslims are to abstain from eating, drinking, smoking, and engaging in sexual intercourse. During the month of Ramadan, fasting is one of the Pillars of Islam, making it one of the most important acts of worship.
The Qur’an mentions that fasting was prescribed for those before them (Jews and Muslims) and that by fasting, a Muslim gains taqwa. Taqwa can be described as the care taken by a person to do everything God has commanded and to keep away from everything He has forbidden.8 Essentially, fasting helps prevent sin while also instilling a sense of fraternity and solidarity.
Intermittent fasting is different from religious fasting, yet it still has ties to humanity’s past. Ancient hunter-gatherers did not have supermarkets, refrigerators, or sustenance readily available. As a result, humans evolved to be able to function without food for extended periods of time. The act of fasting is actually more natural for homo sapiens than eating 3 meals a day.9
Intermittent fasting is an eating pattern that cycles between periods of eating and fasting. Many people “fast” while they sleep, so intermittent fasting can be as simple as extending that fast longer into the day. Skipping breakfast is one method used to prolong a fast. There are many types of intermittent fasting, so knowing your body and seeking guidance from a health professional can help target the type of fast that is best suited for you.
Types of Intermittent Fasting
Different types and methods of intermittent fasting have emerged, including:
- The 5:2 Diet: 2 days a week, individuals only eat around 500-600 calories.
- Eat-Stop-Eat: Once or twice a week, individuals do not eat anything from dinner one day until dinner the next day (a 24 hour fasting period).
- The 16/8 Method: Individuals fast for 16 hours a day, for example, from 8 PM one day to noon the next day.
- The Warrior Diet: This was popularized by fitness expert, Ori Hofmekler. Individuals eat small amounts of raw fruits and vegetables during the day and eat only one large meal at night.
- Spontaneous Meal Skipping: Individuals skip meals when not hungry and eat balanced meals during the non-fasting periods.
Benefits of Intermittent Fasting
Researchers have studied intermittent fasting for decades. Study findings are often contradictory and inconclusive, but evidence shows that intermittent fasting may provide the following health benefits:
Eating during a set period can reduce the number of calories consumed, and it could boost metabolism. A study conducted in 2017 found that intermittent fasting led to greater weight loss in men with obesity than a regular calorie restriction.10 Additionally, research from 2016 concluded that a 16/8 approach for 8 weeks showed a decrease in fat mass.11
Studies suggest that intermittent fasting can help prevent:
- Type 2 Diabetes
- Heart Conditions
- Some Cancers
- Neurodegenerative Diseases
A 2017 study on animals concluded that intermittent fasting reduced the risk of nonalcoholic fatty liver disease and cancer. Other studies reported that intermittent fasting reduced glucose 3-6% in those with prediabetes and also decreased insulin by 11-57% after 3 to 24 weeks of fasting.12
Extended Life Span
Scientific animal studies have suggested that intermittent fasting can lead to a longer lifespan. For example, one study reported that short-term repeated fasting increased the lifespan of female mice.13
The National Institute on Aging mentioned that, even after decades, scientists still cannot explain why fasting lengthens lifespan. As a result, they cannot confirm the long-term safety of this practice.14
Thinking and Memory
A recent study showed that intermittent fasting may have a bigger brain payoff than a small degree of calorie restriction (10%): specifically, better memory retention and brain cell proliferation.15 Other studies have concluded that intermittent fasting boosts working memory in animals and verbal memory in adults.
What to Expect When Intermittent Fasting
Matt Mattson, PhD. and a professor at the John Hopkins University School of Medicine and former chief of the Laboratory of Neurosciences at the National Institute on Aging, says, “During the fasting period, the cells go in kind of a stress-resistance mode. And then when you eat, they’ve prepared themselves to quickly take up nutrients, proteins, and grow. However, the transition can be tough on your body.”16
While waiting a bit longer between meals may be fairly simple, there may be side effects as your body gets used to intermittent fasting, such as:
- Your stomach will most likely grumble during fasting periods.
- You could potentially dehydrate since you aren’t eating. Make sure to drink lots of water.
- You’ll probably feel tired at the beginning of your intermittent fasting journey because your body is running on less energy than it’s used to.
- Since fasting can boost stress levels, you might find that your sleep pattern is disrupted. Try adopting a healthy sleep routine to combat this issue.
- Due to lack of salivary flow and the rise of acetone, you could experience bad breath.
- During the first few days of intermittent fasting, you may experience headaches or lightheadedness.
- The same biochemistry that regulates your mood also regulates your appetite with nutrient consumption affecting neurotransmitters like dopamine and serotonin. This could potentially play a role in anxiety, depression, and irritabilty.17
Seek Your Doctor’s Approval
Considering that the bulk of intermittent fasting studies have been conducted on animals or in short periods on humans, researchers and physicians recommend always seek a professional’s advice before proceeding.
Intermittent fasting is not recommended for those who are:
- Struggling with weight gain
- Below the age of 18
- Pregnant or breastfeeding
- Suffering from dementia or immunodeficiencies
- Susceptible to eating disorders16
Intermittent fasting is not for everyone. If you have any concerns or adverse effects, consult with your doctor.
Let us know, have you tried intermittent fasting before? Which method? Any advice for people just beginning intermittent fasting? Share in the comments section below.