There are two different issues here for refeeding:
- Avoiding pain. When you refeed, you want to start taking in food as fast as your body allows. Depending on the length (if shorter - like 3 to 5 days) you might be fine with some sauteed greens and a regular meal an hour later. Longer fasts might be better broken with some Kimchi - wait an hour - some greens - wait an hour - 4 ounces of meat - wait an hour and then eat the rest of a regular meal (i.e. just more meat and greens). You are simply trying to avoid gastrointestinal distress (which you might get anyway - even under this kind of scheme).
- Ensuring your body that you are not in food scarcity (to avoid metabolic slowdown). From the time you start refeeding you want to ensure you are not restricting calories. If your regular Keto day is around 2400 calories then, if eating 3 meals a day - start 800 with calorie meals - if 2 times a day - start with 1200 calories meals. Do not try to keep the number on the scale low by keeping calories low. Also, you want to avoid binging. It is very easy to start eating after a multi-day fast and have trouble stopping. You may have been thinking about all the foods you were going to break the fast with for many hours or a couple of days. You want to avoid the urge to “go wild” - not just because you are losing some of your gains but also, it can lead to becoming upset with yourself and you can fall into a spiral of overeating for a while.
It might be best to think of a (for example) 5-day fast as 8 days of controlled eating.
- One day before the fast starts to ensure you are eating what you normally would on Keto. Specifically avoiding the “last meal” mentality. Having a big meal just before fasting really means your fasting is actually starting later (i.e. an 800 calorie breakfast and then fasting is very different from a 2400 calorie OMAD sized meal - which really means your fast is starting the next day).
- Five days for fasting.
- Two days of forcing yourself to stick with your normal meals on Keto (i.e. if you were averaging 2400 calories on Keto in the weeks leading up to the fast - cap your daily intake at 2400 for the 2 days following the fast). The reason is that - right after a fast - if you follow something like “moderate protein and fat to satiety”, you might really mess up. Think of the couple of days after a multi-day fast as time when you can’t trust your satiety signals.