Intermittent fasting has become a trendy way to lose weight, thanks to buzz on social media and endorsements from celebrities like Gisele Bundchen, Kourtney Kardashian, and Jennifer Aniston. But despite its current flavor-of-the-month status, intermittent fasting has actually been around for thousands of years. Here’s a look at intermittent fasting and its progression over time.
Fasting has played an important role in the development of countless civilizations looking to improve physical fitness, increase mental health, and explore spirituality. Everyone from the ancient Greeks to Native Americans to Buddhist monks engaged in this age-old practice, which still exists today in a variety of forms and is used for a range of reasons.
DailyOM spoke with experts to find out more about intermittent fasting through the ages until today.
What Is Intermittent Fasting?
Intermittent fasting is a type of dietary lifestyle that involves alternating periods of fasting with periods of eating and drinking.
There are three main types of intermittent fasting windows. They include:
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Time-restricted intermittent fasting. When practicing time-restricted fasting, a person limits food consumption during specific hours of the day. For example, you set an eating window of 8 (or 12) hours, and then fast for the other 16 (or 12 hours) of the day.
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Complete fasting. This is a form of intermittent fasting when a practitioner does not eat at all on certain days of the week, while on other days, they eat whatever they choose without restrictions.
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Modified fasting. This is when a practitioner eats a reduced-calorie diet for a few days of the week, then eats whatever they want for the remaining days, such as two days with modified fasting and five eating more “regularly.”
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Who Practiced Intermittent Fasting?
Throughout the course of history, many populations have adopted intermittent fasting — and for a wide variety of reasons. As early as the fifth century BCE, Hippocrates recommended fasting to help patients heal from certain illnesses. It was also common for ancient Greek athletes to fast before the Olympics to strengthen their bodies for the games. Shamans from the Siberian Evenk tribes fasted in order to see visions, control spirits, and communicate with the dead during training sessions. The Pueblo Indians abstained from eating and drinking to mark seasonal changes and major life ceremonies.
Intermittent fasting has also played an important role in many different religions. Muslims first began fasting for a whole lunar month to celebrate Ramadan over 1,400 years ago. Christians observe a 40-day fasting period during Lent. And members of the Jewish community fast on High Holy Days like Yom Kippur and Rosh Hashanah, as well as when they are in mourning. Buddhist monks also fast after they eat their midday meal, opting for meditation in the evening instead of dinner.
What Was the Original Purpose of Fasting?
Most experts agree that intermittent fasting didn’t start off as a way to shed unwanted pounds. The original motivation was actually far simpler.
“The intention was for religion,” says Jason Fung, MD, a Canadian nephrologist and New York Times bestselling author of The Obesity Code. “People who fasted were considered to be purifying or cleansing themselves, but it was always something that was considered to be very healthy. Intermittent fasting has been around for thousands of years. Fasting is even mentioned in the Bible.”
Who Started Intermittent Fasting for Health?
Although the exact origins of modern-day fasting are still somewhat unclear, it is widely believed that ancient Greek physician Hippocrates was the first person to focus on the use of intermittent fasting to improve health. He was once quoted as saying, “The natural healing force within each one of us is the greatest force in getting well. Our food should be our medicine. Our medicine should be our food. But to eat when you are sick is to feed your sickness.”
Studies show that fasting has been proven to reduce blood pressure, lower coronary artery disease, and improve cognitive function. According to the American Heart Association, not only can regular fasting lead to lower rates of heart failure, but also to a longer life span.
How Fasting Changed Over Time
Although fasting began as a spiritual practice and is still used across a wide range of religions, today intermittent fasting is also a popular weight loss tool. Just scroll through your Instagram feed on any given day and you’ll find dozens of hashtags for #intermittentfasting.
That is due to larger-scale changes in our modern diet, particularly over the past century, when processed food became more and more accessible. “Even in the 1950s, where we were starting to see an abundance of food, portion sizes were still small compared to today,” says Martica Heaner, adjunct association professor of nutrition at Hunter College in New York City. “Restaurants closed early, so there weren’t a lot of takeout and delivery options. People had more set meal times. So, naturally, people ate less and ate in a more disciplined and structured way. As more of the population became overweight and obese in the last century, losing weight became more of a focus.”
Enter intermittent fasting, which practitioners say is a simple-to-follow way to be mindful about eating without too many rules or a too-rigid structure.
“The research is pretty clear,” says Heaner. “All forms of intermittent fasting are a way to cut calories. When you eat less, you lose weight. It’s that simple. It’s really just an easier approach for some people to cut calories without having to count them or obsess about it too much.”
“Intermittent fasting is really just any period of time where you don’t eat,” says Dr. Fung, who runs an intermittent fasting clinic in Toronto, Canada. “Your body stores the calories that you eat as glucose or blood sugar. Both of those are sources of energy. When you eat, you’re taking in more energy than you can use. When you don’t eat, your body takes those calories back out of storage and uses them for energy. That’s literally why you have body fat, to store energy. Over time with fasting, your body burns off some of that fat source.”
The Bottom Line
Intermittent fasting isn’t for everyone. If you’re pregnant or breastfeeding, or you struggle with disordered eating, this may not be the best approach for you. Studies show that fasting can actually be detrimental in these types of scenarios and potentially do more harm than good.
That said, rest assured that this isn’t just another trendy new diet craze. People have routinely, for short periods of time, abstained from eating and drinking over the course of thousands of years. So, regardless of whether you prefer to fast a few days a week, long stretches every day or shorter stretches for only a few hours a day, this eating plan is completely customizable.
“There is no magic,” says Fung. “You can do whatever you like. If the 16:8 hour schedule works best for you, then do that. If the longer fasts work best for you, then you can do that. And, of course, you can switch between schedules and do a longer fast occasionally and shorter ones more often. Just do whatever is giving you the best results.”
