How many hours of fasting is okay?

Author: Moshe Weissnat  |  Last update: Friday, May 30, 2025

For example, studies have found that people who regularly fast more than 16 or 18 hours a day have a higher risk of gallstones. They're also more likely to need surgery to remove the gallbladder. Eating for 12 hours and then fasting for 12 hours is likely safe for most people, Longo explains.

How many hours of fasting is healthy?

As with most eating plans, it's always a good idea to speak to your doctor before overhauling your diet, Hyer says. That's especially true if you take medications or have health problems or if you're considering more extreme fasting plans. But for most people, she says, a fast of 12 to 14 hours is a pretty safe bet.

Is it better to fast for 12 or 16 hours?

If weight loss is a primary goal, a 16-hour fast may be more effective. However, if you're looking for a more sustainable fasting routine, a 12-hour fast may be a better fit. Ultimately, the best fast duration for you is the one that meets your needs and is something you can achieve.

How many hours is a true fasting?

Simply put, it means you stop eating completely, or almost completely, for a certain stretch of time. A fast usually lasts from 12 to 24 hours, but some types continue for days at a time. In some cases, you may be allowed water, tea, and coffee or even a small amount of food during the “fasting period.”

What is the ideal fasting length?

Some experts may recommend females fast for 14 hours and slowly build their way up to 16 hours, while males can start fasting for 16 hours straight away. This type of intermittent fast may be helpful for someone who has already tried the 12-hour fast but did not experience any benefits.

Best Time of Day to Fast? (Morning or Evening?) 2024

Does coffee break a fast?

If you are fasting for weight loss or metabolic health, then coffee or even coffee with non-insulinogenic (insulin-spiking) additions like butter, coconut oil, or heavy cream should not break your fast. However, milk, flavored creamer, sugar, and many other sweeteners will break your fast, no matter your goals.

What is the best fast hours?

Depending on your lifestyle and when you can manage to stop eating, the best hours for intermittent fasting include the 16/8 or 14/10 fasting periods. Intermittent fasting is hailed by many as the new mantra of weight loss, disease prevention, and reversal of aging.

How many hours should I fast before a blood test?

You usually need to fast for 8 to 12 hours before a test, but your provider will tell you exactly how long to fast. For certain tests, you may be asked not to drink alcohol for a longer period of time. If your blood test requires fasting, you can usually schedule the test early in the morning.

How much fasting is too long?

Longer periods without food, such as 24-, 36-, 48- and 72-hour fasting periods, are not necessarily better for you, and may be dangerous. Going too long without eating might actually encourage your body to start storing more fat in response to starvation.

Does sleep count as fasting?

FAQs. Does fasting still count when you're sleeping? Fasting is the practice of abstaining from food, so it doesn't matter what you're doing as long as you're not eating. You can still benefit from fasting even if the majority of your fasting period is while you're asleep.

How long should I fast to lose belly fat?

The 16/8 method is a good starting point, where you fast for 16 hours (including the time you're asleep) and then eat during an 8-hour window each day. To ease into it, begin with a shorter fasting period, like 12 hours, and gradually extend it as your body adjusts.

What stage of fasting burns the most fat?

What is the most effective fasting time window? Fat burning typically begins after approximately 12 hours of fasting and escalates between 16 and 24 hours of fasting.

Why am I not losing weight on 16:8 fasting?

You may need a longer or shorter eating window, or you may want to try out a new protocol entirely. Decrease (or increase) your calorie intake within your fasting window. Aim for 7–9 hours of sleep. Cut back on processed foods.

Is fasting good for your liver?

Conclusions. By re-synchronizing the circadian clock and re-setting key metabolic pathways involved in cell proliferation, growth, defense and function, intermittent fasting is able to prevent the evolution of chronic liver disease towards liver cancer.

Can I brush my teeth before a fasting blood test?

It's generally acceptable to brush your teeth while fasting before blood work, as long as you avoid swallowing any toothpaste or mouthwash. However, it's advisable to use plain water for rinsing rather than toothpaste to minimize the risk of inadvertently consuming substances that could affect test results.

How long should you fast for weight loss?

Fasting did seem to spur noticeable short-term weight loss, the researchers found. People who fasted for five days lost about 4% to 6% of their weight; those who fasted for seven to 10 days lost about 2% to 10%, and those who fasted for 15 to 20 days lost 7% to 10%.

What happens if you don't fast 12 hours before blood work?

Not fasting before a standard lipid panel blood test may also throw off the LDL cholesterol number. But newer methods to measure LDL may mean you don't need to fast. In contrast, eating does not significantly affect measurements of total cholesterol and HDL (good) cholesterol.

Why is 16 hours the magic number for fasting?

During the 16-hour fast, your body undergoes a process known as autophagy, a process where the body destroys old or damaged cells in the body. Autophagy recycles the cells that help in the reduction of inflammation in the body and reduces diseases.

Can you chew gum while fasting?

Consuming 1-2 pieces of regular gum may not be an issue for more laid back fasting methods. But still, if you chew enough gum, the gum you chew has more sugar than normal, or your body is more sensitive to sugar, it may be enough to evoke an insulin response and break your fast.

Does coke zero break a fast?

So, can you drink Coke Zero while fasting? The answer largely depends on your goals and how your body responds to artificial sweeteners. From a calorie standpoint, Coke Zero won't break your fast. However, if you're fasting for insulin sensitivity, gut health, or autophagy, you might want to think twice.

What happens if you accidentally drink coffee while fasting?

Black coffee is almost calorie-free. A typical cup contains about 3 calories and no fat, protein, or sugar—the things that might “break” a fast by triggering digestion or changing your metabolism. So, drinking plain black coffee during fasting periods is perfectly fine.

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