Ekadasi is an auspicious day, which is noted twice per month (11 days after the new moon and 11 days after the full moon) in which one is freed from sins when observing it by abstaining from eating grains and pulses. That is, nothing of wheat, corn, rice, beans etc. as the collective sins of the planet takes shelter of these food items on these days. If one is suffering from any disease of the body, it will increase on these days, if the above items are consumed, as they act like a sponge soaking up the water element in the body and remain in the stomach as ama (undigested food matter). Not only does one gain health benefit from avoiding the forbidden items, but Ekadasi increases one’s spiritual inclination and merits. All other foods and fruits can be taken. The next day the fast is broken, by again taking grains and beans/pulses as normal.
One does not have to follow the Hare Krishna path to benefit from this observance. This is the beauty of Vaisnava culture.
Here is a link to guide you to the days on which Ekadasi appears:
“After the merciful Supreme Lord thought over what He had previously considered, He suddenly manifested from His own form the deity of the lunar day Ekadasi.’ (Padma Purana 7.22.27) Afterwards the different sinful living entities began to follow the vow of Ekadasi and were then elevated quickly to the abode of Vaikuntha. Oh my child Jaimini, therefore the lunar day of Ekadasi is the self-same form of the Supreme Lord, Visnu, and the Supersoul within the heart of the living entities. Sri Ekadasi is the utmost pious activity and is situated as the head among all vows.”
“Therefore those persons who are serious about the ultimate benefit for the soul will never eat grains on the Ekadasi tithi/day. According to the instructions of Lord Visnu, every kind of sinful activity that can be found in the material world takes its residence in this place of foodstuff (grain and beans) on Ekadasi. Whoever follows Ekadasi is freed from all sins and never enters into hellish regions…”