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What Can You Eat While Fasting?

Updated: Aug 9, 2021

Dr. Johnson frequently recommends time-restricted eating to her patients as a very beneficial way to increase longevity and obtain optimal health.

One of the most common questions patients ask Dr. Johnson is what foods can be ingested while fasting. Essentially, the answer is: any food that contains 0 calories. But fasting doesn't have to be a painful struggle, there are many ways to incorporate different flavors while remaining in a fasted state.

fasting, water, gum, circadian rhythm

First, what is time-restricted fasting?

Time-restricted eating is technically a form of intermittent fasting. But not all intermittent fasting is considered time-restricted eating. Time-restricted eating is based on decades of research by Dr. Satchin Panda of the Salk Institute. Time-restricted eating differs from your normal fasting in that it is based on the theory of circadian biology. Essentially, your eating and fasting cycles should follow that of the sun, you should only eat during the daylight hours and fast once the sun sets.

The concept of eating only during daylight hours is based on several biological factors:

  • The circadian rhythm regulates the metabolic processes within the cell. In the morning, as the sun rises, your metabolism is at its peak. So eating a big meal in the morning will quickly be metabolized to provide energy for the rest of the day. But if you eat a big meal in the evening, when the metabolism slows, the likelihood that the food will be stored as fat increases.

  • The liver metabolizes glucose during the daylight hours and halts overnight. Glucose metabolization is strongest in the morning and weakens throughout the day.

  • Cells are much more sensitive to insulin during the day and less so at night. This is because melatonin will inhibit the release of insulin from your pancreas. Melatonin produced in the gut goes directly to the pancreas and modulates the secretion of insulin. For most people, the secretion of melatonin begins 3 hours before you go to bed.

  • The circadian rhythm is responsible for managing biological functions like cellular repair and hormone signaling. If you eat in sequence with the rhythm, hormones like cortisol and thyroid will all function properly.

A time-restricted eating lifestyle is not difficult to incorporate into your lifestyle, as 7-8 hours of the fast are done while you are sleeping. You should begin your morning with the biggest meal of your day. From your first bite, the 12-hour countdown starts. Lunch should be slightly smaller than breakfast, with dinner being your smallest meal of the day. Regardless of when you have your first meal, you want to make sure that your last meal is at least three hours before bed. Dr. Johnson recommends switching up your fasting routines several times a week- follow a time-restricted eating pattern for 5 days a week. The other two days can shorten the fasting window to around 8-6 hours.

Health benefits of time-restricted eating:

The health benefits of time-restricted eating were first documented by Dr. Panda in his 2018 study on mice following this eating pattern. Two groups of mice were fed the same high-fat diet, but while one group of mice could eat all day long, the second group was restricted to an 8-10 hour window. The group that followed restricted eating hours became lean, fit, and healthy, while the other group of mice gained weight and developed symptoms of metabolic disease like high cholesterol, fatty liver, and diabetes. Keep in mind, these differences are only caused by the difference in eating hours, the mice were fed identical diets. Further studies on humans following time-restricted eating have found beneficial effects such as a decrease in blood glucose, blood insulin, and fat mass.

Dr. Johnson strongly believes that time-restricted eating is the most beneficial form of fasting routine to follow. But research has demonstrated time and time again that fasting, even not in accordance with the circadian rhythm, has a multitude of benefits. Such benefits include:

So, what foods can you eat without breaking your fast?

Fasting can be difficult. Especially if you want to explore longer fasts like the One Meal a Day fast (where you eat one meal a day and fast for the remaining 23 hours) or the 36 hour Monk Fast (where you fast for 36 hours once per week), restricting yourself of all sustenance can be very difficult. But of course, the most important part of fasting is drinking enough water!

In fact, water is one of the only things you can ingest while fasting. So, you might find yourself drinking more water when you’re fasting. Adding small amounts of salt to your water throughout the day can help keep your electrolyte levels high.

Luckily, if you get bored of water, there are several other types of foods you can eat that will not interrupt your fast.

Coffee- To be specific, black coffee with no additives will not break your fast, it might actually increase the benefits. One study found that coffee triggered autophagy in mice, which is a biological process that cleanses the body of dead cells and increases immune function. Bulletproof coffee or coffee with added sugars or dairy products will break your fast. This is because, in its purest form, black coffee has essentially no calories. The additives in any other type of coffee will halt the fasting process and trigger the beginning of the circadian clock.

Gum- Sugar-free gum with very low calories will not break your fast. However, some types of gum contain up to 30 calories per serving, which can add up and break your fast. But chewing sugar-free gum while fasting can actually help your fast by decreasing hunger and appetite. This is because chewing gum while fasting increased satiety and stabilized levels of a hormone that decreases appetite.

Tea- This is another beverage that will not break your fast, as long as you’re drinking plain tea with no added sugars. In fact, some teas can help you throughout your fast. Drinking green teas can assist with digestion. Teas with yerba mate and turmeric can keep your energy levels high. And teas with lavender and chamomile can aid in sleeping on an empty stomach.

Sparkling water- As with tea and coffee, sparkling water is fine as long as there are no calories or sugar. Sparkling water can also help you feel more full and satiated as you fast. Further, sparkling water is just as effective in hydrating the body as regular water. Just be sure to check the nutrients label of your sparkling water to ensure you aren’t accidentally breaking your fast.

Bone broth- There is actually a specific type of fasting that involves only drinking bone broth for an extended period of time. As, bone broth can help support autophagy and help to revitalize the digestive tract. But for longer fasts, drinking small amounts of bone broth will rejuvenate your body with valuable nutrients. Most bone broths only contain around 15 calories per ½ cup.

Lemon juice- Adding lemon juice to your water, tea, or sparkling water is another great way to add some flavor to your fast. According to some fasting experts, lemon juice will actually help your fast, as it aids digestion and boosts your immune system. This will allow you to more quickly enter a state of deep fasting. Moreover, the fiber in lemon juice will help you feel more full even as you’re fasting.

However, any amount of calories you ingest will, in fact, break your fast. As, most foods will have other nutrients that will trigger your body’s digestive process. Luckily, as long as you stay under 50 grams of carbs while you’re fasting, you’ll remain in ketosis. Which will allow your body to continue burning fat.

Further, keep in mind the research behind breaking a fast with certain foods is still not 100% fleshed out. If you’re doing short fasts like time-restricted eating, it’s probably best you avoid everything but water to ensure the beneficial effects.

The best foods to break your fast:

When breaking your fast, especially one over 15 hours, it’s critical to take into consideration what foods you will eat. It’s best to ease out of your fast with foods that are easily digestible. Immediately eating a meal high in sugar, fat, or fiber can lead to bloating and discomfort as your body struggles to digest it. Below are some of the best foods to break your fast:

  • Smoothies: A blended drink will gently reintroduce nutrients into your body. Especially using fruits that have had their skins removed, as that’s where most of the fiber is contained.

  • Soups: Soup with protein and easily digestible carbs like tofu or lentils are a great way to break a fast. Especially ones with a bone broth base. Avoid soups with heavy cream or ones with high-fiber contents.

  • Vegetables: Cooked potatoes and other soft, starchy vegetables are beneficial for breaking a fast.

  • Healthy fats: Foods like eggs and avocados with lots of healthy fats are easily digestible and can be very beneficial in breaking a fast.

  • Fermented foods: Kefir, sauerkraut, and other fermented foods are great for breaking a fast and boosting gut health.

Please check with your physician before implementing a fasting protocol.

While time-restricted eating can be a very beneficial eating regime to follow, the most beneficial dietary plan is one based on your unique genomic sequence.

Through DNA testing, we can precisely identify the patterns and imbalances of your unique metabolism and use nutrients to suppress the expression of disease, illness, and other unhealthy patterns. If you're interested in genomic testing, click here to learn more! Or contact our office at

The Johnson Center for Health services patients in-person in our Blacksburg and Virginia Beach / Norfolk locations. We also offer telemedicine for residents of Virginia and North Carolina!