Fasting, everyone does it to a certain degree and some take it to an extreme. Every night, after having your last meal or snack you start to fast. In the morning you break the fast by eating breakfast. Some people eat first thing in the morning while others wait a few hours. The same goes for the last meal. Some eat seconds before going to sleep while others stop eating several hours before. 

Does fasting time matter?

Most people naturally fast without thinking about it between 8-12 hours every day. Although fasting has been around for a long time, intermittent fasting or IF, has recently become popular. Intermittent fasting extendeds the fasting period by several hours and consolidates all three meals into a 6–8-hour window. 

Longer fasts can last from one day to one week. Some religious fasts, such as the Muslim Ramadan, last all day with one large meal after the sun sets. There are also health spas around the world that offer medically guided fasting. 

With so much variance in fasting durations, it is difficult to decide what is the best option for you when it comes to improving your health. 

The most popular fast currently for weight loss is the intermittent fast. It allows a 6–8-hour window to eat all the food you want until your time is up. Many people have successfully lost weight while following intermittent fasting and have found it to be a sustainable lifestyle.

Aside from weight loss, many people, historically, fast to improve the health of their body. In simple terms, the fasting process puts metabolic stress on the body and increases the body’s resilience to future stressors, such as disease. 

Think of it as working out and gaining muscle through putting the muscle under physical stress of weightlifting, running, etc. 

So, does fasting for a longer time result in better health or is a few extra fasted hours plenty to reap the benefits? 

Based on the evidence, 1-2 day fasting per week with normal eating on non-fasting days offers the most promise for long-term health and body resilience to stress of disease, aging, etc. However, there is evidence that intermittent fasting on a daily basis can improve our body’s resilience as well. 

Fasting longer than 3 days requires medical supervision as it poses serious medical risk, not to mention that these long-term fasts are extremely difficult to follow. Also, there is little advantage to longer term fasting beyond 2 days. 

The Key Takeaway

Short-term fasting of 1-2 days per week has the greatest impact on our body’s long-term health and improves our body’s resilience to disease as we age. Many people have easily gone a whole day without eating due to work and a busy lifestyle.

Increasing the fasted state to 16 hours or more per day through intermittent fasting also has shown to be beneficial and tends to be easier to follow for most people. Ideally, the eating window should follow the natural circadian rhythms of light and dark, avoiding eating during early and late hours. 

Intermittent fasting can easily be applied to most people’s lifestyle by simply not eating before 9am and after 5pm. Enjoying a cup of coffee or tea in the early waking hours and soothing/calming tea in the evening hours is a good way to get your mind off eating. 

You may even find you have more energy by not eating shortly after waking and get a better night's sleep by not eating before bed. 

Important considerations before starting to fast:

• Do not exceed fasting for more than 3 days

• Do not fast 1-2 days if you fall under any of the following:

  • Pregnant or breastfeeding 

  • Underweight 

  • Sick or have an infection

  • Advanced liver or kidney disease

  • Uncontrolled hypothyroidism

• Intermittent fasting is safe for most people if adequate calories are consumed on a daily basis

• Check with your doctor if you have any medical conditions prior to starting to fast

• A dietitian can determine what type of fasting is best for you, set up a plan to ensure adequate nutrition and calorie intake, and improve adherence through creating accountability in the early stages

If you are interested in adding fasting to improve your health or have questions about fasting, schedule a consultation with me or feel free to email me at adamskowyra@dietitian2go.net.

Written by Adam Skowyra MPPD, RDN, LD