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How to Intermittent Fast (The Healthy Way)

We hear a lot about intermittent fasting and all of its many benefits. But, if you don't know the right way to fast, you could be missing out on key benefits and potentially doing more harm than good to your body.

In this blog, we'll break down how to intermittent fast, how to exercise while fasting, what you can eat while intermittent fasting, and who should avoid fasting altogether.

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Fasting 101:

There are multiple different ways to intermittently fast, some better than others. Some common forms of fasting include:

  • 5:2 Fasting- This fast allows you to eat normally for 5 days and then restrict calories on the other two days to 500 or 600 calories per day.

  • Whole-Day Fasting- This approach allows you to eat once a day. Some people eat dinner and then wait to eat again until dinnertime the next day.

  • Alternate-Day Fasting- In this fast, you fast every other day- with the fast consisting of 25% of your calorie needs (around 500 calories). On non-fasting days you can eat normally.

  • Time-Restricted Fasting- This is Dr. Johnson's preferred way to fast. It gives you an eating window of 8-12 hours and then you fasti for the remainder of the day.

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. So, if the sun rises at 6 am and sets at 6 pm, you can eat between those 12 hours.

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 eating window to around 8-6 hours.

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:

Fasted exercise:

A fasted workout is pretty self-explanatory- it’s simply working out while you’re also in a period of fasting. But how long do you need to go before entering this fasted state? It’s usually defined as 8-12 hours without food. However, depending on how efficient your digestive system is at processing food, it could take as little as 3-6 hours.

When you’re in a state of fasting, your body has stopped breaking down food and insulin levels have dropped. There is also no available glycogen in your blood for your body to use as fuel. This forces your body to find another source of energy- usually fat. Moreover, lowered insulin levels will also allow body fat to be easily broken down and oxidized (burned) as free fatty acids.

Working out while fasted has many benefits, including:

  • Increased endurance

  • Greater fat-burning potential

  • Increased growth hormone

  • Improved insulin sensitivity

  • Weight loss

  • Easy on the GI tract

The most important thing to keep in mind when working out while fasting is what kind of workout you choose to do. Experts agree that you should only do light, low-intensity cardio workouts while fasting. You should avoid any type of high-intensity interval training, boot camp, or CrossFit classes. And you should especially not weight lift or do strength training while fasting.

Before jumping into a fasted workout, you should tread carefully at first to ensure your safety. Further, if you want to burn body fat and retain your fitness level, you should follow these tips below!

  • Stay hydrated → When you’re fasting, water is your best friend. Not only will it keep you hydrated all day long, but it is also one of the few things you can consume while fasting. Some experts recommend drinking more water while fasting.

  • Boost your electrolytes → While fasting, and especially while working out fasted, you should make sure to keep your electrolytes up. This can easily be done by adding some sea salt to your water!

  • Keep the duration and intensity low when doing long fasts → If you’re doing a fast 24 hours or more, you should stick to walking, yoga, pilates, and other low-intensity workouts.

  • Eat a meal after your workout → You should follow your fasted workout with a healthy, protein-heavy meal!

***For people with certain medical conditions, working out while fasting may not be the best choice. You should make sure to check with your doctor before beginning this new fitness regime. Moreover, if working out while fasting leaves you light-headed or nauseous, it may not be right for you.***

What can you eat while fasting?

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 from all forms of 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

  • Gum

  • Tea

  • Sparkling water

  • Bone broth

  • Lemon juice

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.

How to break a 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.

Who should NOT fast?

Unfortunately, fasting is not for everyone. Several groups should not try intermittent fasting, these include:

  • Women who are pregnant or trying to become pregnant (extended periods of fasting may throw off your menstrual cycle)

  • Individuals taking diabetes medication (fasting often causes the sharp drop of blood sugar during long periods without food)

  • Women who are breastfeeding (fasting while breastfeeding could potentially threaten a child's development, due to the lack of available nutrients)

  • People under the age of 18 (during this important stage of development, your body needs as much food and nutrients as it can get)

  • Those engaging in intensive training or trying to build muscle (depriving your body of nutrients during intense physical training can inhibit muscle growth and repair)

  • People on multiple types of medications (food, or lack thereof, can affect your dosage and absorption rates)

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!


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