I gave up on fasting for weight loss as well. It's just another form of caloric restriction and that just doesn't work for me. My body is just too efficient: it immediately turns down the metabolic rate to adjust.

I've done 5 days fast, 2 days feeding for a month straight and didn't lose any weight that I didn't immediately regain upon the 2 feeding days.

What is your diet like when you come out of fasting? Are you refeeding for a few days and restoring electrolytes before you go for a heavy meal?

Irregular to say the least. Sometimes there's a big meal/event and I just gorge on crap - end up with stomach pains. Other times it's a regular lunch at home: lots of veggies, whole grains and protein (this has better impact on stomach).

I've found that there's a sweet spot as to fasting length: too soon (say a day) and I feel really hungry, so calorie count probably doesn't add up as I eat more than I 'saved'. Wait too long and the something similar happens (starving), my ideal spot seems to be ~3 days and breaking the fast with a 'regular'/not-eating-out meal.

I don't supplement for the fasting, from what I've read ~3 days isn't long enough to warrant that. Just lots of water and some salt (iodized) if I'm doing 4 days. Usually headaches may show up at the end of the 3rd day but that just tells me I'm not hydrating properly (also piss color helps get feedback on this).

May I suggest using Celtic sea salt instead of iodized or Himalayan? It really helps with absorbing the water into mucus membranes. It also has a bunch of other special properties.