How Long Does It Take to Have an Empty Stomach?


By Dr. Mercola

The question posed in the headline is a common one heard by doctors everywhere: “How long does it take to have an empty stomach?” It’s an important question for anyone taking prescription drugs because what you eat and drink, as well as the timing of your meals, can affect the way certain medications work.

Beyond that, there is value in becoming aware of the health benefits associated with regularly emptying your stomach. If your first thought, when you hear the words “empty stomach,” is a negative one, it’s time to update your thinking. Not only can you survive on an empty stomach, you can also thrive.

In my experience, emptying your stomach as a daily habit — through intermittent fasting or another safe type of fasting — can boost your health and well-being. The effects can be so radical that you actually may be able to reduce (or potentially eliminate) your use of prescription drugs as your health improves.

Taking Medications? How Do You Know When Your Stomach Is Empty?

“Ask Well,” a medical question and answer feature presented in The New York Times,1 recently fielded this inquiry: “Many medications should be taken on an empty stomach. How do you know when your stomach is empty?”

Dr. Richard Klasco, assistant professor of emergency medicine at the University of Colorado School of Medicine, who provided the answer, wrote, “Two hours after eating is a crude rule of thumb. A more accurate answer depends on the drugs you are taking and your medical conditions.”2

Klasco goes on to note that research on gastric emptying — the length of time it takes for your stomach to return to empty after a meal — has been going on since the 1940s.

Over the years, the experiments have changed based on scientific and medical advances. Since 1966, nuclear medicine, which involves the use of a small amount of radioactive material to emit photon energy, has remained as the established standard for measuring gastric emptying. Says Klasco:3

“Standards for such testing have been set by the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine. They state that a normal stomach should be 90 percent empty after four hours.4

The difference between this standard and the earlier study probably reflects differences in foods. Solids take longer to digest than liquids; fats take longer to digest than protein or carbohydrates. The [U.S.] Food and Drug Administration [FDA] … defines an empty stomach as ‘one hour before eating, or two hours after eating.'”

Klasco indicates the FDA’s two-hour rule is only an estimate, which means your stomach “will probably not be completely empty” after two hours, he asserts.5 In addition, Klasco points out that the expectations for an empty stomach vary widely from drug to drug.

It’s best, he says, to read the package insert that accompanies all prescription medications dispensed in the U.S. and to clarify any uncertainties with your doctor. The insert contains, Klasco says, each drug’s FDA-approved prescribing information.

It is often found glued to the drug package in the form of a tightly folded, fine-print flyer.”6 For easier reading, you may want to review the insert details online at DailyMed, a website operated by the U.S. National Library of Medicine — a branch of the National Institutes of Health (NIH) — that contains more than 105,000 detailed medication listings.7

With respect to stomach emptying and medications, Klasco notes some medical conditions, like diabetes, can delay gastric emptying, whereas a bariatric surgery can accelerate it.8 Again, check with your doctor to find out the best emptying guidelines for your particular situation.

How Fasting Positively Affects Your Mitochondria and Your Health

By far, the best and quickest route to an empty stomach is to stop eating, otherwise known as fasting. This simple act of forgoing food for a certain period of time not only ensures stomach emptying, but it has also been validated as a powerful lifestyle tool for combating insulin resistance and obesity, as well as chronic diseases like cancer and many other health problems.

Not only does fasting upregulate autophagy and mitophagy — two of your body’s natural cleansing processes necessary for optimal cellular renewal and function — but it also triggers the generation of stem cells. Beyond that, cyclically abstaining from food and then initiating refeeding also massively stimulates mitochondrial biogenesis, the process by which new mitochondria are created.

Mitochondria are the powerhouse of your cells, producing about 90 percent of the energy being generated in your body. Because energy is needed to support nearly every bodily process, without healthy mitochondria you will be more vulnerable to illness and disease.

Your mitochondria also act as the coordinator for apoptosis —programmed cell death — an important process to ensure the death of malfunctioning cells that might otherwise degenerate into cancer. There’s even evidence suggesting fasting can help prevent or even reverse dementia because it helps your body clean out toxic debris.

The reason for this is because when autophagy increases, your body starts breaking down and recycling old protein, including the beta amyloid protein in your brain that is believed to contribute to Alzheimer’s disease. While water-only fasting can be extremely beneficial for those struggling with excess weight and/or Type 2 diabetes, compliance can be difficult.

Fortunately, research has confirmed that similar results, while not as profound, can be achieved through intermittent fasting. This type of fasting entails following a meal-timing schedule where you’re fasting for at least 16 hours every day and eating all of your meals within a six- to eight-hour window.

Are You Caught in a Cycle of Grazing and Snacking? Fasting Can Help

In the event you’ve not yet considered trying intermittent fasting, I would like to once again remind you of the tremendous health benefits associated with this practice. You may be avoiding intermittent fasting because you associate “fasting” with starvation or simply because it seems too daunting and challenging to make the necessary adjustments.

As mentioned, the goal with this type of fasting is to forego food for at least 16 hours a day. As such, you will want to skip either the first or last meal of the day. (I recommend the first meal.) As such, you will consolidate all of your calorie intake into the remaining block of eight or fewer hours.

I have had great success with intermittent fasting and highly recommend you take your first meal at around lunchtime. I also advise you avoid eating anything at least three hours before you go to bed. The concept of intermittent fasting is still catching on in the U.S., a country plagued by all-day grazing and the continuous availability of food around the clock.

While grocery stores and restaurants used to close by 8 or 9 p.m., many establishments now remain open until midnight and some 24 hours a day, seven days a week. Authors of a 2017 study published in the journal Nutrients, reviewing 35 years of snacking behavior by American adults, stated:9

“Results show that snacking remains a significant component of the U.S. diet and the foods consumed at these snacks — sugar-sweetened beverages, desserts and sweets and salty snacks — are not the types of foods recommended by the U.S. dietary guidelines.”

If you realize constant snacking is crippling your health, please review my “Intermittent Fasting Infographic” for more information about this style of eating and the recommended time windows you can establish. If forgoing eating for 16 hours seems overwhelming at first, set a smaller goal and work your way up.

If your experience is anything like mine, the hours you set aside to give your body’s digestive and other systems a break from food will produce health benefits beyond your imagination. In time, as you begin to realize some of the health benefits, you will likely become more motivated to do intermittent fasting on a regular basis.

The Health Benefits Available From Intermittent Fasting

When done well, intermittent fasting delivers a number of impressive health benefits. You will undoubtedly discover others that are meaningful to you beyond what is listed below. Research proves intermittent fasting:10,11,12

Boosts your cognitive function — Intermittent fasting improves your cognitive function by providing your brain with its preferred fuel: fat instead of glucose.

Studies indicate intermittent fasting helps in the prevention of Alzheimer’s disease and Parkinson’s because of the boost in brain-derived neurotropic factor (BDNF), a protein that is both neuroprotective and brain-stimulating.

Minimizes food cravings and hunger pangs — While you may think you’ll be starving your body through fasting, the truth is it is a helpful technique known to eliminate cravings and reduce hunger pangs. It does this mainly by moving your body away from dependence on glucose for energy.

Normalizes your insulin and leptin sensitivity — Your body’s blood sugar level is closely regulated not only by insulin, but also by leptin. Both hormones influence your food intake and weight, as well as your risk of chronic diseases such as diabetes.

As mentioned, intermittent fasting shifts your body away from being dependent on glucose, which then curtails your sugar cravings, thus normalizing your insulin and leptin sensitivity.

Promotes cellular regeneration — Intermittent fasting promotes cell regeneration by triggering autophagy, a natural, “self-eating” process your body uses to recycle damaged cells. It helps inhibit cancerous growths and the development of chronic disease.

If you are eating throughout the day every day, your body has very little time for repair and renewal. By giving it a break from eating, your body can shift its focus to growing new cells, cleaning up cellular debris and removing toxins — activities it cannot perform otherwise.

Shifts your body to burn fat for fuel — Limiting your food intake forces your body to switch away from glucose to burning fat as a source of energy. This shift often results in weight loss and may lead to other improvements based on the fact fat is a more efficient and longer-burning fuel.

Contraindications Associated With Intermittent Fasting

To be successful with intermittent fasting you will want to ensure your doctor approves and that you do not have a serious medical condition for which it would be contraindicated.

By the way, fasting beyond 24 hours is not recommended for children. A better way to help a child lose weight is to restrict or remove refined grains and sugary foods from their diet. Fasting may not be recommended if you are:

Malnourished — If this is your situation, you will want to put your focus on eating healthier, more nutritious food and adding supplements as needed

Pregnant or breastfeeding — As a mother you need a continual supply of nutrients to ensure your baby’s healthy growth and development; fasting could put both the health of you and your baby at risk

Taking medication — If you’re on medication, check with your doctor before taking up fasting. That said, even if your doctor approves, you’ll need to take care with medications that must be taken with food.

Metformin, aspirin and similar drugs can cause stomach upset or stomach ulcers when taken on an empty stomach. The risk of trouble is especially high if you’re on diabetic medication.

Underweight — If you have a body mass index (BMI) of 18.5 or lower, fasting is not safe for you because it may increase the stress on your body and/or cause you to lose more weight.

Tips to Ensure Your Success With Intermittent Fasting

While you can simply restrict your eating window to eight or fewer hours while continuing to eat and drink whatever you want, you’ll get a lot more out of fasting if you:

Drink plenty of water and other healthy liquids — During fasting, make sure you’re getting enough liquids to keep yourself feeling full and satisfied. Drinking clean, pure water and beverages such as organic coffee and tea — in moderation — will help curb food cravings, especially as you first begin fasting.

As you might imagine, drinking alcohol, energy drinks, soda and other unhealthy beverages would be counterproductive to fasting.

Eliminate processed foods from your diet — One of the advantages of fasting is detoxification. As such, you’ll realize more health benefits by eating whole foods such as organic vegetables, healthy fats and grass fed meat.

By eliminating processed foods from your diet, you will support your body in healing and detoxification.

Incorporate exercise into your daily routine — Working out in a fasted state can deliver amazing results. Without a ready supply of glucose and glycogen from which to draw — because it has been depleted over the course of your fasted state and has yet to be replenished — your body is forced to adapt and pull from the only energy source available: fat stored in your cells.

Some of the types of exercise I recommend include: high-intensity interval training, stretching, walking, weight training and yoga.

Make sleep a high priority — Getting about eight hours of quality sleep a night will do wonders for your health. Most adults are chronically sleep-deprived, which has numerous negative health effects, including increasing your risk of accidents and chronic diseases like diabetes and cancer.

Receive support from your friends and family — It is important for you to have the support of your friends and family, especially the people with whom you live, as you undertake intermittent fasting. These folks can share the journey and encourage you in moments of weakness when you may be tempted to give up.

With some thoughtful planning and careful consideration, you can empty your stomach and unleash a whole new level of health through intermittent fasting.

For even better results and to maximize your fat-burning potential, I suggest you combine intermittent fasting with a cyclical ketogenic diet. For all the details on how to do this, please refer to my article “Why Intermittent Fasting Is More Effective Combined With Ketogenic Diet.”