Is Fasting Good For You?

autoimmunity autophagy calorie-restricted diet chronic disease electrolyte balance insulin resistance intermittent fasting religious fasting type-2 diabetes water fasting weight loss Feb 22, 2025

A wooden plate with utensils arranged like clock hands showcases a vibrant medley of vegetables, salmon, egg, and avocado. The word "FASTING" borders the left side of the plate.

Dieting for weight loss is incredibly common. It’s been estimated that 45 million Americans go on a diet each year, spending billions of dollars on programs and products in support of their goals. At the same time, more Americans are overweight than ever, with the prevalence of obesity reaching 40 percent in 2023. Why?¹

Most weight-loss diets involve reducing your calorie intake over a period of time, and some diet plans recommend restricting certain foods or food groups as well. But there’s a problem with this approach.²

Restricting calories lowers your basal metabolic rate (BMR) — the number of calories your body burns at rest. Eventually, your body simply adapts to the reduced caloric intake by reducing calorie usage. However, fasting — abstaining entirely from food — promotes fat burning while helping your body maintain its BMR. This key difference makes fasting a powerful tool for sustainable weight loss. It’s why, in recent years, fasting has captured the attention of doctors, dietitians, and even celebrities.^3,4

Fasting isn’t a one-size-fits-all method though. In this article, we’ll explore its different forms, their benefits, and possible risks:

What is fasting?
Religious fasting
Intermittent fasting
Water fasting

Wondering if fasting is a good fit for YOUR lifestyle and goals? Read on!

What is fasting?

At its core, fasting means going without food and drink for a set period of time. Typically, a fast lasts from 12 to 24 hours. But some types of fasting can extend for days. And in some protocols, you’re allowed to drink water, tea, and coffee — or even eat a limited amount of food — during the fasting period.^5,6

When you fast, you focus not on what you eat, but when you eat. So, rather than strictly tracking calories or restricting food groups, you follow a structured eating schedule.⁵

If you’ve just begun fasting, you’re probably going to feel hungry. That’s completely normal — you’re used to regular food intake, after all. But after a few days, your body adjusts, making those hunger pangs more manageable.⁶

Fasting has been a part of human culture for millennia, although it wasn’t always a conscious choice. In ancient times, our hunter-gatherer ancestors often went without food for long periods while foraging. Over time, fasting evolved from a necessity into a deliberate practice, becoming deeply rooted in religion for many people.^6,7

Religious fasting

Many of the world’s major religions include fasting as a spiritual practice. One in five Americans fast at specific times of the year for religious reasons.^6,8,9

Many Christians, especially Catholics, observe fasting periods throughout the year, including the 40-day Lent, which leads up to Easter. On Ash Wednesday and Good Friday in particular, strict Catholics may eat only one full meal and two smaller meals that, when combined, do not equal a regular meal. Also, everyone aged 14 and up abstains from meat on these days. Fasting and abstinence are meant to foster self-examination, repentance, and spiritual renewal among Christian believers.^10,11

For Jewish people, fasting is required on Yom Kippur (the Day of Atonement), the most sacred day of the year. Males over the age of 13 and females 12 and older abstain from all food and drink for 25 hours. In Judaism, fasting is a way to seek forgiveness for one’s sins and achieve spiritual purification.^11,12

During the holy month of Ramadan, Muslims abstain from food and drink from sunrise to sunset, using the time for spiritual reflection and worship. In Islam, fasting is viewed as a way to purify the soul and strengthen one’s connection with Allah.^11,13

In Buddhism, lay practitioners often fast during retreats and other periods of intensive mediation. They stay away from animal products (except for milk) and processed foods. They also abstain from the “five pungent foods” — garlic, Welsh onion, wild garlic, garlic chives, and asafoetida — which are believed to stimulate the senses. Buddhists practice fasting as a means to cultivate self-control and reduce attachment to physical desires.^11,13

For health and safety, some groups of people are generally exempt from religious fasting — and other types of fasting, for that matter. They include children, pregnant or nursing women, and malnourished individuals. People with chronic conditions, such as abnormal blood sugar levels, high or low blood pressure, and heart disease, might need to avoid fasting too. Fasting isn’t recommended for people with a history of an eating disorder either.^10,12,14

Beyond religious practices, many people today follow another popular type of fasting called intermittent fasting, with the goal of managing weight and improving overall health.

Intermittent fasting

Intermittent fasting (IF) involves cycling between periods of eating and fasting. It’s not about starving yourself — rather, you cut back on calories for short, defined periods. Plus, during IF windows, you can drink water, tea, black coffee, and other non-caloric beverages. The idea is that, over time, your body adjusts to smaller portions and craves fewer unhealthy foods — as long as you stick to a healthy diet when you eat.¹⁵

There are several common approaches to IF, the most popular one being the 16/8 or 14/10 method. In this time-restricted approach, you fast for 16 or 14 hours and eat within an eight- or a 10-hour window each day. For instance, a common schedule for 16/8 is only eating between 10 AM and 6 PM; for 14/10, the eating window is from 9 AM to 7 PM. Since most people already fast while sleeping, this method feels natural, making it a safe bet if you’re interested in trying IF for the first time. Think of it like extending your overnight fast by skipping breakfast the next day and starting dinner slightly earlier.¹⁵

Then there’s the 5:2 method, where you limit your calorie intake to 500 calories for two days a week. Usually, you have a 200-calorie meal and a 300-calorie meal on fasting days. The key is to focus on foods high in protein and fiber to keep yourself full. The days of fasting are up to you, as long as they’re not back to back. For example, you can choose to fast on Tuesdays and Thursdays, then eat a regular, healthy diet the other five days.¹⁵

Another option is alternate-day fasting — a “modified” fast every other day. This means you still consume around 500 calories on fasting days, then go back to your regular, healthy diet on non-fasting ones.¹⁵

If you’re looking for a more intense version, you can go for zero calories on fasting days in the 5:2 or alternate-day fasting protocol. In fact, this stricter variation will be more effective, given the reduced benefits of calorie restriction over complete abstinence.

Lastly, there’s the eat-stop-eat method, which involves fasting for a full 24 hours once or twice a week. Think fasting from breakfast to breakfast or lunch to lunch. Then, on non-fasting days, you resume a regular, healthy diet.¹⁵

IF has gained recognition for its health benefits besides weight loss. One of the most important advantages of fasting is the stimulation of autophagy — your body’s cellular recycling system. During this process, your cells break down and repurpose older tissues, especially proteins, into new versions. Research suggests that autophagy may play a key role in preventing and fighting diseases. It’s also important for getting rid of the saggy skin that may accompany significant weight loss.^16,17

Autophagy ramps up after about 12 hours of fasting, peaks at around 16 hours, and falls off after around 24 hours without any calories. This timeframe is a major reason why intermittent fasting is more effective than other forms of fasting.

The perks of IF don’t end there. This fasting method has been shown to reduce insulin resistance, lowering blood-sugar levels and helping fight type-2 diabetes. Some studies show that IF also lessens inflammation, which drives many chronic illnesses. Last but not least, IF boosts the production of brain-derived neurotrophic factor (BDNF). This hormone promotes the growth of new nerve cells, helping protect against cognitive decline.¹⁵

Keep in mind that IF can have side effects, especially when you’re just starting out. For one, it can make you “hangry” (hungry and irritable). Also common are headaches and dizziness, which are actually symptoms of dehydration. This is why proper hydration and adequate electrolytes (especially potassium) are crucial during a fast. Himalayan pink salt is a great supplement to stave off hunger and avoid headaches when doing IF.^15,18

Other initial drawbacks of IF include low energy levels, sensitivity to cold, and reduced performance. These will typically dissipate after a few rounds of IF.¹⁵

Water fasting

Some people take fasting a step further with prolonged water fasting. In this more advanced method, you consume only water for two days or more. It’s crucial that the water be of high quality, with electrolytes to prevent dehydration and support your body’s natural cleansing processes.⁸

Research on water fasts lasting 5 to 20 days has shown promising results. Prolonged water fasting promotes ketosis — a state in which your body burns fat instead of glucose for energy. This process reduces both fat mass and abdominal fat, leading to weight loss. Other benefits of prolonged fasting include improved blood pressure, better liver health, reduced blood sugar levels, and enhanced insulin sensitivity.^8,19

But going without food for multiple days can take a toll on your body, particularly in the initial stages. You can experience headaches, dizziness, insomnia, and a dry mouth. Other concerns are possible muscle loss and electrolyte imbalances. Plus, prolonged fasting can drive hormonal changes as your body adapts to the lack of food. This is why people who are underweight, or those with low blood pressure or heart conditions, may be at higher risk of complications when fasting for long periods.^8,19

If you’re considering prolonged water fasting, be sure to consult with a doctor first, especially if you have any underlying health problems. There are fasting clinics that provide medical supervision for prolonged water fasts, which can reset your immune system and even reverse some autoimmune conditions.²⁰

Conclusion

So, is fasting good for you? The short answer is YES. Whether you’re looking to lose weight, boost your metabolism, or improve your overall health, fasting can offer significant benefits — as long as it’s done mindfully.

Like any lifestyle change, the key is to choose a fasting method that aligns with your individual health needs and goals. Remember: What worked for another person might not work for YOU!

It’s always a good idea to consult with a professional before you begin any fasting regimen, especially if you have any existing health conditions. They can guide you on the safest and most effective approach, as well as monitor your progress along the way.

Ready to unlock the power of fasting with an expert’s guidance and support? Sign up to Maximize Your Performance and book your private consultation today!

References

Is Fasting Good For You?

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