Did the modern LDS idea of fast offerings have extra-Mormon roots? [LDS] members are encouraged to fast once a month on Fast Sunday and to give the money they save by not eating two meals to the church; those who can afford to be more generous are encouraged to give more than simply the money saved as a fast offering.

So given that the biblical root of the concept of a fast offering is the exhortation of Isaiah:

Is not this the fast that I have chosen? to loose the bands of wickedness, to undo the heavy burdens, and to let the oppressed go free, and that ye break every yoke?
Is it not to deal thy bread to the hungry, and that thou bring the poor that are cast out to thy house? when thou seest the naked, that thou cover him; and that thou hide not thyself from thine own flesh?  (Isaiah 58:6--7)

And that Joseph Smith introduced the current LDS practice of using the cost of the meal foregone by fasting to support the poor in Kirtland (as later reiterated by the interregnal Council of the Twelve in these words):

Let this be an example to all saints, and there will never be any lack for bread: When the poor are starving, let those who have, fast one day and give what they otherwise would have eaten to the bishops for the poor, and everyone will abound for a long time; and this is one great and important principle of fasts approved of the Lord.  (History of the Church 7:413)

Is there a separate modern root or inspiration of this practice?  It doesn't seem to be derived from patristic or medieval Catholicism or Reformation practices as far as I know (which, admittedly, isn't a lot in the area of devotional practices).  Specifically, was this something the Shakers, the Campbellites, or another Restorationist group influential on early Mormonism practiced?
As far as I am aware of, no there are no other modern roots to this practice.

The practice of fasting and then giving offerings to the Lord is very old. 


  Judges 20:26 Then all the children of Israel, and all the people, went up, and came unto the house of God, and wept, and sat there before the Lord, and fasted that day until even, and offered burnt offerings and peace offerings before the Lord.


But it's vs 27 that is more interesting in the context of our current question. 


  27) And the children of Israel enquired of the Lord .... 28) saying, Shall I yet again go out to battle against the children of Benjamin my brother, or shall I cease? And the Lord said, Go up; for tomorrow I will deliver them into thine hand. (emphasis mine)


While the offerings part is usually what gets the most attention. The true reason to fast is to show humility and self discipline before the Lord and then ask the Lord some pressing question.

And just as they did in Israel, LDS often go to the temple during or soon after a fast.   

LDS don't tend to make a big deal of it, but they often fast far more then just the one day a month, depending on their needs, desires or trials.

On different occasions of great trial in an LDS community, the Bishop (head of one congregation) or even Stake President (head of many congregations over the bishops) may ask the members to fast for a special purpose. 

On these occasions a fast offering is not paid. Though a member could pay it if they so desired.