Intermittent Fasting 101: What It Is, How It Works, and Its Benefits

Intermittent fasting, often misunderstood as starvation, is a practice that can be done without discomfort or hunger. When done well, it can bring about the positive health changes you seek, without the negative connotations associated with starvation.

What Is Intermittent Fasting?

Intermittent fasting, a flexible eating pattern, involves alternating periods of fasting and eating. It's not about restricting certain foods or food groups, or limiting calories. This flexibility is what sets it apart from traditional diets, giving you more control over your eating habits.

Intermittent fasting is more than just a diet, it's an eating pattern that aligns with your body's natural rhythm. It's about refraining from eating for extended periods, with different plans defining fasting and eating periods in a way that suits your body's needs.

Whole-Day Fasting

As the name suggests, whole-day fasting involves complete fasting for one to two days per week. In some variations of this plan, individuals may eat a small amount of up to 25% of the normal calorie intake on fasting days. Otherwise, only water, coffee, and other zero-calorie drinks are allowed.

On non-fasting days, people on this plan eat normally without restrictions.

Alternate-Day Fasting

Alternate-day fasting is similar. Alternating a fasting day on Monday, such as an eating day on Tuesday, creates more structure in designating caloric intake on particular days. Like whole-day fasting plans, alternate-day fasting can entail a complete fast or significantly reduced calories.

Another variation of alternate-day fasting is the 5:2 plan. The "5" in this plan refers to five days a week when a person eats normally without restrictions. A person fasts completely or significantly restricts calories for the remaining two days.

Time-Restricted Feeding

One of the most popular forms of intermittent fasting is time-restricted feeding. This structure designates specific hours of the day for fasting and feeding, rather than specific days, making it a more manageable approach for many.

The most common time-restricted feeding schedules are the 16/8 or 14/10 plans. On these plans, a person fasts for 14-16 hours daily. They consume all their calorie needs during the remaining 8-10 hours.

The Warrior Diet

The Warrior Diet, another form of intermittent fasting, is all about balance. It's not just about when you eat, but also what you eat. This balance of food choices and timed feeding creates a distinctive eating plan that can reassure you about its health benefits.

On the Warrior Diet, individuals eat some raw fruits and vegetables early in the day. Then, they "feast" on a large dinner of whole foods.

This diet-and its name-derives from practices of ancient warriors. Like Warrior Dieters, these warriors ate little during the day. After all, during this time, they trained and battled enemies. However, when the day's battles were done, they enjoyed a large feast to prepare for the next day.

In terms of food choices, the Warrior Diet is similar to the paleo diet.

Spontaneous Meal Skipping

Some people are intrigued by intermittent fasting but have yet to be ready to make a structured commitment. These individuals can ease into the practice with spontaneous meal skipping. Without designating particular times or days as fasting periods, people can use their hunger as a guide. On this plan, individuals skip meals when they don't feel hungry.

How Does Intermittent Fasting Work?

Calories equal energy, and your body needs energy to work. However, the body can adapt when you deprive your body of energy from calories.

Burning Fat: Helping Your Body to Access Stored Energy

One way the body adapts to reductions in caloric intake is by looking elsewhere for energy. When you fast, your body looks to fat stores for energy.

To make these fat stores more readily available, the body adjusts hormone levels. In particular, levels of human growth hormone (HGH) increase. As HGH increases, fat stores decrease, and muscle mass increases.

Lower insulin levels or reduced insulin sensitivity also help the body access energy stored as fat.

Importantly, the body's response to intermittent fasting differs from its response to other types of fasting. During extended periods of caloric restriction, like starvation diets, your body can adapt to calorie restrictions. Eventually, this adaptation-while suboptimal-allows the body to function on fewer calories. As a result, fat burning gradually slows or even stops.

Intermittent fasting, in contrast, keeps the body off balance. Periods of fasting and feasting prevent the body from adapting to any energy level. Thus, the body continues to shift to fat-burning as an energy source when calories become scarce.

Cellular Autophagy: A Cleaner Body Uses Energy More Efficiently

Besides using energy stored as fat, your body adapts to caloric restrictions by becoming more efficient. When you fast, you prompt your cells to "clean house."

The word "autophagy" comes from the Greek "auto," which means "self," and "phagein," which means "to eat." In the process of cellular autophagy, your cells clean themselves by eating themselves. In other words, cells identify and remove old and worn-out parts. These include proteins and structures, like organelles and cell membranes.

By removing this build-up and replacing worn-out parts with new ones, your cells become more efficient energy users.

The hormone glucagon is responsible for stimulating cellular autophagy. Fasting is, in turn, responsible for increasing glucagon levels. Glucagon levels increase as insulin levels decrease. Thus, fasting decreases insulin levels, increases glucagon levels, and prompts cellular autophagy.

Gene Expression: Following the Body's Instructions

Intermittent fasting also affects the body by changing gene expression. Gene expression refers to the process by which cells implement the instructions built into our DNA.

Gene expression allows the body to use these instructions to adapt to its environment. As they adapt to environmental changes, your body's cells turn various genes on and off. They also produce different proteins depending on their needs.

When you fast, your body exhibits positive changes in gene expression related to longevity and immune response.

What Are the Benefits of Intermittent Fasting?

Many people investigate intermittent fasting as a tool for weight loss, and the method is promising. However, intermittent fasting benefits extend much further.

Weight Loss

To lose weight, you need to burn more energy than you consume. On your part, this generally means decreasing calories and increasing activity. It can also mean increasing the metabolic rate of your body. Intermittent fasting acts on each of these factors.

Reduced Calories

You eat fewer meals When you engage in intermittent fasting. Of course, your meals tend to be larger and contain more calories than any one meal. However, most people have a limit to how much they can comfortably consume in one sitting. Thus, your "feasting" periods on an intermittent fasting plan are still likely to include fewer calories than your previous eating habits.

Increased Energy

As your body adapts to intermittent fasting, you are also likely to experience increased energy. Feeling tired after eating is common and normal. After all, your body needs energy to digest the food you just consumed. When you follow a traditional three-meal-a-day plan, you'll likely experience this tiredness at least thrice daily.

When you follow an intermittent fasting plan, however, you will most likely eat your largest meal in the late afternoon or evening. Fortunately, this is precisely when you expect to feel tired and want to get a good night's sleep. Thus, any sleepiness associated with your "feast" meal is a bonus.

Increased Metabolism

Finally, intermittent fasting can speed up your body's metabolism. In one study, intermittent fasters increased their metabolism by 3.6-14%. Increased metabolism, in turn, promotes weight loss.

Decreased insulin sensitivity and increased levels of HGH and other hormones promote an increased metabolism. As we saw, intermittent fasting produces each of these effects.

Thus, research shows that intermittent fasting can promote weight loss through each of these mechanisms.

Fat Loss

Losing weight can benefit a person's overall health. However, losing the right kind of weight is even more important. The greatest health benefits derive not from weight loss but from fat loss. Here again, intermittent fasting is a powerful tool.

When you consume more energy (i.e., calories) than you expend, you add to your fat stores. These fat stores are excess energy, but the calories you eat daily remain your body's go-to energy source. Your body will only burn stored fat if you provide enough energy from calories.

To burn fat, you must force your body to look elsewhere for energy. During fasting periods, the bodies of intermittent fasters must do just that. Without calories coming in, your body fuels itself by burning its fat stores. Increased levels of HGH promote fat burning.

Importantly, it also promotes muscle mass. This highlights another advantage of intermittent fasting over continuous caloric restrictions, which can cause muscle loss.

Better Sleep

Most people design their intermittent fasting plans around other important aspects of their daily schedules. These include work and sleep. On many intermittent fasting plans, fasting periods coincide with sleeping periods. Because active digestion can interfere with sleep, intermittent fasting can create ideal sleeping conditions.

On a 16/8 plan, for example, an individual might eat most of his or her calories during the afternoon and early evening hours. Such a schedule allows adequate time for digestion before bedtime.

Sleep and intermittent fasting can further complement one another as intermittent fasting promotes precisely those cellular repair processes that go on in your body while you sleep.

Protection from Disease, Inflammation, and the Effects of Aging

Your body constantly interacts with and adapts to its environment. In doing so, it attempts to maintain homeostasis, or internal balance and physical well-being.

Environmental factors threaten this balance, and negative health consequences can result if the body cannot deal with them.

Free radicals are among these threats. Highly reactive free radicals create cellular oxidation, which can damage other important molecules. These include proteins and DNA.

Damage from oxidative stress and inflammation is a significant factor in aging and a host of chronic diseases. Intermittent fasting may allow the body to respond more effectively to oxidative stress. It may also fight inflammation. In these ways, it can promote overall health and longevity.

Besides protecting against damage from oxidative stress, intermittent fasting promotes mechanisms that fight common chronic illnesses.

Intermittent Fasting and Type 2 Diabetes

By reducing insulin resistance and fighting obesity, intermittent fasting may reduce your risk of developing Type 2 diabetes.

Studies in animals also show that intermittent fasting can protect against kidney disease, especially as a complication of diabetes.

Individuals at high risk of developing Type 2 diabetes may find intermittent fasting beneficial.

Intermittent Fasting and Heart Disease

Heart disease is the leading cause of death worldwide. Risk factors for heart disease include:

1. High blood pressure
2. High cholesterol
3. High triglycerides, or fatty acids
4. High blood sugar levels
5. Certain inflammatory markers
6. Obesity

Intermittent fasting shows promise to improve each of these factors.

Intermittent Fasting and Cancer

By promoting cellular autophagy and protecting against oxidative stress, intermittent fasting keeps your cells working efficiently. Proper cell function, in turn, protects against cancer.

The increased metabolism you experience on an intermittent fasting plan may further enhance these potential anti-cancer effects.

Intermittent Fasting and Brain Health

Intermittent fasting's ability to stimulate cellular autophagy may also protect against Alzheimer's disease. Likewise, intermittent fasting's potential to promote nerve growth may protect against Parkinson's and Huntington's disease.

Finally, intermittent fasting may promote brain health and protect against depression by increasing hormones that may be deficient in the brains of depressed patients.

Overall Longevity

With the above benefits, intermittent fasting has the potential to increase lifespans.

Additional research on the relationship between intermittent fasting and human longevity is needed. However, animal studies show staggering benefits. In one study, rats on an intermittent fasting plan lived 83% longer than rats in the control group.

Intermittent Fasting: A Fast-Track to Better Health and a Longer Life?

The potential benefits of intermittent fasting are encouraging. The body of research documenting them is growing. Nevertheless, more research is needed. Furthermore, it is important to remember that intermittent fasting results vary across individuals.