How Many Hours Should You Fast?

One of the questions I get asked most frequently is, “how many hours should I fast?” Well, that depends on what health benefits you are hoping to achieve.  The longer you fast, the more the benefits add up. 

However that doesn’t necessarily mean longer is better for everyone. For example, if you’re hoping to increase ketones, a 17 hour fast may be what you need, however if you’re trying to heal a musculoskeletal injury, you’ll want to work your way up to a 72 hour fast. And of course, if you’re new to fasting, read my Beginner’s Guide to Fasting

 Here are the benefits of fasting broken down by hours fasted:

13-15 hour fast

A 13-15 hour fast is considered intermittent fasting and if you are new to fasting, this is where you’ll want to start. At 13 hours fasting, your body will secrete growth hormone. The growth hormone assists in burning fat and slowing down the aging process. If you are looking for an anti-aging solution I recommend this level of fasting. 

15 hour fast

This is when most people begin to create ketones. Ketones are a sign that your liver has moved burning sugar to burning fat for energy. Furthermore, ketones are neuro protective and will go up to the brain, giving you energy and better mental clarity. 

17-24 hour fast

Fasting offers the following benefits: cellular repair, detox, cancer prevention, fut repair, aids with anxiety and depression, and brain and memory loss.

17 hour fast

When you reach 17 hours without eating you will start to stimulate autophagy. What this means is your cells intelligence has been turned on and they are able to repair themselves. This is best for people with autoimmune conditions. 

24 hour fast

At 24 hours, your intestinal cells reboot and GABA production occurs. GABA is the neurotransmitter known to relax our brain and help with anxiety. Our gut health is incredibly important in preventing autoimmune disorders and aiding in weight loss.. 

36 hour fast

The more you fast, the more it forces your body to burn glucose, insulin, and toxins that are stored in fat. I always say that it is better to have fat around your muscles than around your organs and this length of fast will force your body to burn stored glucose and insulin.  36-48 hour fasts is where to start to see fat loss, anti-aging, and an increase in dopamine.

48 hour fast

At 48 hours you begin to reset dopamine receptor sites. If you are feeling like your happiness level is not where it needs to be this is where you need to be. 

72 hour fast

This is a 3 day fast when you feel like you just do not know what to do anymore. I have seen these fasts used for people with severe injuries and diagnoses that want to reboot their whole immune system where healing starts. At 72 hours your stem cells for the immune system are regenerating as well as stem cell production for musculoskeletal injuries. 

Watch my full Youtube video to figure out which fast will work best for you, and download my fasting benefits chart that provides guidance on the benefits during each type of fast. 

In health,


2020-08-13T00:58:26+00:00Fasting Techniques, Health|


  1. julie August 8, 2020 at 4:57 pm - Reply

    I’m fasting for 72 hours just water and black coffee in the morning,but my keto stick test shows only trace or none, I’ve hit the 63hr. mark am i still getting all those great benefits , just not burning fat?

  2. Quang Minh Pham September 24, 2020 at 3:18 am - Reply

    i’m fasting 16 hours 5 days a week and want to try the 24hrs to activate the autophagy. Please advise how often I should do the 24hrs fast?

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