The Big Idea
Christians, Muslims, and many other religious groups have observed periodic fasting for millennia. This practice originated as a means of spiritual purification, but mounting research shows that periodic fasting is generally healthy and that it can be used for weight loss, cardiovascular health, and longevity.
The longest-lived populations are associated with some form of periodic fasting: namely the Ikarians, whose island is also called ‘the place where people forget to die’, the Seventh Day Adventists in the Loma Linda area, and the Mormons of Salt Lake.
What it is
Periodic fasting is fasting periodically – not daily. The term ‘periodic fasting’ is often confused with ‘intermittent fasting’, but the two are mostly separate concepts.
Periodic fasting is larger in scope than intermittent fasts and it usually occurs on a weekly, monthly, or yearly scale. (Think: Ramadan, Lent.) Intermittent fasts are more about the daily balance of eating and fasting.
The most common periodic fasts can involve total or partial abstinence from food, and they include
- 24-hour fasts
- two-day fasts
- prolonged fasts
- fasting-mimicking diets
- and Daniel fasts.
People typically choose periodic fasting as a means for more weight loss or greater health effects than can be achieved through shorter intermittent fasts.
Blood pressure and heart health
Significant blood pressure reductions were observed in a 21-day Daniel Fast involving 43 healthy men and women between 20 and 60 years of age. A population study in Utah reported similar blood pressure enhancement, with hypertension being less frequent in people who fasted compared to non-fasters. These decreases in blood pressure were also seen alongside drops in other risk factors for heart disease, including cholesterol, weight, and diabetes.
Fasting speeds up your body’s metabolism in order to convert fat into energy through the processes of ketosis and gluconeogenesis. Eons of famines and food shortages have adapted humans to live without food for days, weeks, and months – even for over a year, in the longest case of fasting known to science.
Weight loss has been seen in all forms of periodic fasting, including 24-hour fasts, prolonged fasts, and Fasting Mimicking Diets. Scientists believe that some types of periodic fasting have a regulatory effect on the circadian rhythm – which positively impacts metabolism and body composition. But the consensus is that most fasting methods burn fat through calorie deficits.
Relationship with food
Though many believe that fasting would be harmful to those with clinical eating disorders, the research has shown no evidence of that being the case. In fact, most people who’ve tried a periodic fast say that they have a better relationship with food. This is because fasting forces you to question the root of your hunger: is it emotional? out of boredom? or is it actual, factual hunger?
Learning to go without food for longer periods helps you discern what ‘true hunger’ is and helps you to avoid patterns of emotional eating.
Though inflammation has many causes, scientists have determined that elevated levels of growth hormone and insulin-like growth factor 1 (IGF-1) are contributors to the inflammatory process. The constant consumption of protein (especially in excessive amounts) raises IGF-1 to inflammatory levels that can lead to injury or illness.
During fasts, protein is eliminated or reduced, and IGF-1 levels drop down to healthy ranges. Health experts recommend periodic fasts to promote immunity and reduce inflammation.
Elevated levels of IGF-1 are associated with cancer and early death. In a study done on 184 people in their 90s, it was found that those with the lowest levels of IGF-1 had the highest rates of survivability. Fasting is known to reduce IGF-1 levels.
The risks of periodic fasting are low and few, according to most studies. But for periodic fasts of 24 hours or more, there is a risk of
- electrolyte depletion
- and refeeding syndrome (a dangerous electrolyte imbalance that can occur after breaking a prolonged fast).
You should always consult your doctor before trying any fasting regimen, and you should avoid periodic fasting if you have heart disease, liver or kidney disease, or if you are pregnant.
How to Do it
Here’s a breakdown of how to do common periodic fasts:
Abstain from calories of any kind from one meal on Day one, then break your fast with that same meal on Day 2. (Lunch to lunch; dinner to dinner.) Coffee and tea are allowed so long as they’re non-caloric. It can be done once or twice per week.
The same rules for the 24-hour fast apply here: no food and only no-calorie beverages. Typically prolonged fasts last from 2-5 days and doctors advise you to prepare for them with 24-hour fasts and intermittent fasting. Prolonged fasts are usually done once or twice a month.
Fasting Mimicking Diet
The Fasting Mimicking Diet (FMD) is done 5 days per month, and you’re supposed to eat only 25% of your normal calorie intake. The FMD is sold in prepared packages with scientifically formulated meals and supplemented.
The Daniel Fast is a 21-day fast from the Bible where you eat a strictly vegetarian diet. Foods to avoid include
- meat and animal products
- dairy products
- leavened bread and yeast
- processed foods
- solid fats
- and beverages like coffee, tea, and alcohol.
List of Top Science or Studies:
Dr. David Jockers
Dr. Mark Hyman
Author of several best-selling wellness books, Dr. Hyman insists that any plan that eliminates toxic foods (like sugar) is a step in the right direction. From his blog: “On average, every American eats 152 pounds of sugar and 146 pounds of flour each year – all of which converts to sugar…Sugar can actually be eight times more addictive than cocaine. In fact, rats will keep eating sugar even while they get electric shocks that are meant to make them stop! “