Q. What settings should I use for Fasting Threshold & Duration?

A. Let me start with the Fasting Threshold. When you are just starting off the Fasting Threshold assumes more importance. You may not always be able to make you goal fast duration but it is helpful to know when you have skipped eating long enough to be considered fasting. So what is long enough to be fasting? That is the critical question. Basically long enough that your liver and muscle glycogen stores are depleted. The length of time this takes varies dependent on the individual and their activity levels. With prolonged high intensity exercise it could be depleted in a few hours, in a sedentary person it could take up to 24 hours. Perhaps the simplest way to get an indication for a layperson is to monitor blood ketones. Some blood glucose monitors also provide the ability to monitor blood ketones though the strips are more expensive. If you do this a few times then you will have a fair idea of what values to plug in for Fasting Threshold given your circumstances.

If you are on a typical western diet you most likely have no more than six hours (during the day) between your main meals. Probably a lot less if you factor in snacks. It is possible to lower the Fasting Threshold to a minimum of four hours. However as a practical setting this is not very effective. But it may help build your confidence as you grow into longer more sustained fasting.

The main fasting period for most people is still the length of time they sleep for and so as a starting point you could use your average sleep duration as the Fasting Threshold. Literature on fasting indicates that benefits from fasting begin to accrue from adopting a regular fasting period of about eleven hours. Thus, as you become a more accomplished faster, look to increasing your Fasting Threshold towards this level.

The Fasting Duration setting allows you to be aspirational. This is your goal duration for your fast. If you are doing regular intermittent fasting then this number will probably be in the range of 11 to 24 hours. If you are on the 14:10 regime (14 hours of fasting with a 10 hour eating window) then set the fasting duration to 14 hours. If you are on the 19:5 regime set the Fasting Duration to 19 hours to deliver a 5 hour eating window each day. If you want to fast for 3 continuous days each week and eat normally (with daily fasting threshold applied on eating days) for the rest of the week then set the Fasting Duration to 3 days.