Most of us when fasting, even the neighbors will know. Fasting is earnestly seeking to be close to God not to get His things. Isaiah 58:4 What good is fasting when you keep on fighting and quarreling? This kind of fasting will never get you anywhere with me.
God sent Prophet Isaiah to warn the Israelites about their practices. They seem to seek God but just as an act. You can full time at church obeying all practice in the physical but be absent spiritually.
In the Bible, after a fast there was results. When we fast, does it bear fruits. Are we fasting or on a diet.
Job 36:11 If they obey and serve Him, They shall spend their days in prosperity, And their years in pleasures.
These are the principles of God, to obey and to serve Him.
Isaiah 58:5-11 Is this the kind of fast I have chosen, only a day for people to humble themselves? Is it only for bowing one’s head like a reed and for lying in sackcloth and ashes? Is that what you call a fast, a day acceptable to the Lord?  “Is not this the kind of fasting I have chosen: to loose the chains of injustice and untie the cords of the yoke, to set the oppressed free and break every yoke?  Is it not to share your food with the hungry and to provide the poor wanderer with shelter—when you see the naked, to clothe them, and not to turn away from your own flesh and blood?  Then your light will break forth like the dawn, and your healing will quickly appear; then your righteousness will go before you, and the glory of the Lord will be your rear guard.  Then you will call, and the Lord will answer; you will cry for help, and he will say: Here am I. “If you do away with the yoke of oppression, with the pointing finger and malicious talk,  and if you spend yourselves in behalf of the hungry and satisfy the needs of the oppressed, then your light will rise in the darkness, and your night will become like the noonday.  The Lord will guide you always; he will satisfy your needs in a sun-scorched land and will strengthen your frame. You will be like a well-watered garden, like a spring whose waters never fail.