Okay, joking aside....Some believers think we shouldn't eat certain foods, or we shouldn't eat certain foods on certain days. Some believe the Sabbath is on Sunday, others on Saturday, and some believe honoring the Sabbath means simply to allow ourselves to rest in God. All can find A scripture to back-up their views. Who's right? Personally to me it doesn't matter. I do what's right for me based on my knowledge of the Bible, my strength and closeness to God through prayer and praise, my experience and my own wisdom. As my eyes are opened to different things my views on things change....for me. Because everyone is an individual, on their own journey through life, in their own place in events, and with their own experiences and wisdom, we are all free to decide what's right for ourselves. That's the beauty of free will....I don't HAVE to live my life exactly like everyone else.
To me this applies to fasting also. There are so many different types of fasts, that to me, as long as we are living our lives for God, we can't go wrong. God sees our hearts: He sees our struggles and strengths, and He still loves me the same as you, so eh, is the preacher correct? I'll ask God one day if I think of it, but I doubt I will worry about it much until then.
Peace