Ekadashi Upvaas is very important & beneficial for all householders. Pujya Bapuji says that "Upvaas" means Up - Vaas i.e., to stay close to God. The purpose of fasting is to experience peace & bliss. Eating less enables the mind & body to function more effectively. Rules for keeping Ekadashi Upvaas: 1) One should not eat any cereals ("Ann" in hindi) like rice, pulses, wheat etc. & salt.
2)If possible, one should stay on water. Drinking luke warm water or lemon-mishri (crystalized sugar) water is very good as it cleanses the hidden undigested food in the body.
3)If one feels hungry, then one can take milk & fruits. Only banana can be taken with milk. Other fruits should not be eaten with milk (therefore no strawberry shake, mango shake, chickoo shake etc.). One should not eat food like "sabudana", potato chips, fried food, etc.
4)One should think that he/she is keeping this vrat to please God & to progress further in "sadhana" (spiritual practice).
5)One should observe self-control.
6)One should do more of maun-japa (repeating the name of God in mind) in the day time.
7)One should do more of Dhyan & Bhajan by keeping awake for a longer time in the night.
This information comes from http://www.dhyansanjivani.org/upavasa.asp
It is mostly the case that what Hindus call fasting is in fact a form of dieting. This is apparant from these rules as number 3 states that one may eat fruit and (cows) milk.
