What is intermittent fasting, and what are its benefits and harms?
Intermittent fasting is a diet that has become popular and widely used in the health and fitness fields, as well as in the pursuit of achieving an ideal weight.
Many individuals follow the intermittent fasting diet to lose weight, improve their health, and adopt a healthy lifestyle. Furthermore, this diet has been found to have a significant positive effect on the heart and brain, combat aging, and contribute to a longer lifespan.
Some may wonder: What is intermittent fasting? The term "intermittent fasting" is used to describe eating patterns that rely on periods of fasting and eating. It is characterized by its primary focus on meal timing, with few restrictions on the types of foods to be eaten or avoided. Therefore, intermittent fasting typically doesn’t specify a strict diet but rather a schedule of when to eat.
Intermittent Fasting Methods:
Some people follow intermittent fasting as a long-term lifestyle, not just a temporary diet. This is facilitated by the various types and methods available for implementing this eating pattern.
All of these methods involve dividing the day or week into periods of eating and fasting. During the fasting period, the person either consumes small amounts of healthy food or consumes nothing at all except sugar-free liquids.
All intermittent fasting methods promote weight loss by reducing calorie intake, as long as excessive amounts of food are not consumed during the eating periods.
Types of Intermittent Fasting:
12 Hour Intermittent Fasting:
This is ideal for beginners. The 12-hour fast and 12-hour eating window is a good option for those starting intermittent fasting because the fasting period is relatively short, and sleep can be included within the fasting hours, making it easier to follow.
For example, a person could fast from 7 p.m. to 7 a.m., thus spending most of their fasting hours asleep.
16/8 Intermittent Fasting:
One of the most popular methods, it involves fasting for 16 hours and eating within an 8-hour window each day. For example, one could eat between 1 p.m. and 9 p.m., and fast for the remaining 16 hours.
24 Hour Fasting (Eat-Stop-Eat):
This involves abstaining from food for a full 24 hours — for example, from dinner one day to dinner the next day. During the fast, only sugar-free liquids such as water, coffee, and tea are allowed. This method can be practiced once or twice a week.
5:2 Intermittent Fasting:
This involves choosing two non-consecutive days of the week to consume only 500–600 calories, while eating normally on the other five days.
20/4 Intermittent Fasting (The Warrior Diet):
Also called the Warrior Diet, this was one of the first diets to incorporate intermittent fasting. It involves eating small amounts of raw fruits and vegetables during the day, followed by one large meal in the evening within a 4-hour window.
Skipping Meals:
This flexible method involves skipping one or two meals during the day if you're not
hungry or too busy to eat. However, it’s important to eat healthy foods during the remaining meals. This is an unstructured form of intermittent fasting.
The Effects of Intermittent Fasting on the Body:
Intermittent fasting causes various changes at the cellular and molecular levels. These hormonal and cellular changes are responsible for its many benefits.
Some of the changes include:
Human Growth Hormone (HGH): Levels increase, which helps with fat loss and muscle gain.
Insulin: Insulin sensitivity improves and levels drop, promoting fat burning.
Cellular Repair: Fasting triggers cellular repair processes, such as autophagy, where cells remove damaged components.
Gene Expression: Genes related to longevity and disease prevention undergo positive changes.
Benefits of Intermittent Fasting:
Weight Loss: Helps reduce weight and belly fat by promoting fat burning and boosting metabolism.
Blood Sugar Control & Diabetes Prevention: Lowers insulin resistance, reduces blood sugar levels by 3–6%, and insulin levels by 20–31%, lowering the risk of type 2 diabetes.
Heart Health: Improves risk factors such as cholesterol, triglycerides, and blood sugar.
Brain Health: Promotes the growth of new neurons and may help prevent Alzheimer’s disease.
Anti-Aging: May increase lifespan. Studies on mice show a 36–83% increase, though human research is ongoing.
Reduces Inflammation: Lowers inflammation, helping to prevent many chronic diseases.
Side Effects of Intermittent Fasting:
Feeling tired or weak at the beginning.
Heartburn or acid reflux.
Possible effects on fertility in women.
To get the most out of intermittent fasting, it’s important to eat a healthy diet, stick to the permitted eating windows—preferably earlier in the day—avoid fast food, and not overeat during meal times.