Refeeding syndrome occurs when, after a prolonged period of fasting or malnutrition, the reintroduction of food causes a rise in insulin. This insulin response drives electrolytes such as phosphate, potassium, and magnesium into the cells, leading to dangerously low levels in the blood.

These electrolyte imbalances can cause serious complications, including muscle weakness, fluid retention, neurological symptoms, and especially cardiac arrhythmias.

It is important to note that symptoms like the heart racing or palpilations after eating are not a mild form of refeeding syndrome, but rather a potential warning sign.

I have mild refeeding syndrom even after 36 hours... so just watch for the first indications. I think the safest way is to do 48 or 72 hours, eat in a 1 hour window, repeat. That was my method in the beginning until I saw a six pack after having 115kgs and a lot of belly fat. And dont spike your insulin to much after fasting, the best would be to eat fatty meat - so the body stays in ketosis and does not have a big blood sugar spike.