Self-control is good.

Dieting is one very good way to practice self-control.

Fasting is one very good way to practice dieting.

Therefore fasting is good.

Regularity is also a very good way to practice self-control.

Therefore,
fasting on a regular schedule
is very very good.

But Why Ekadashi?

Fasting is beneficial on any day, and even more beneficial on any regular schedule, but the 11th day of each fortnight, “Ekadashi,” is especially fortuitous because that day is consecrated to Vishnu. Hence disciplines practiced on this day have an added benefit of also serving as a means to honor and respect Vishnu.

Is It Just “Grains”?

Fasting, like any discipline, depends on the qualification of the practitioner. One person in a gym can lift 200kg. Another can lift only 20. The first person will not benefit by lifting 20, and the second will not benefit by lifting 200. Similarly, fasting is done according to the ability of the faster. Just like any exercise, you should practice fasting at a level that is challenging, but not extremely difficult.

True fasting is to not even breathe. Only extremely advanced practitioners can practice fasting to this extent.

The next level is to not consume any liquids or solids. This too, is fairly difficult for most.

The next grade is to only drink water. It is not too difficult for most people do to this. Another step down is to not eat any solids. Again, most people with an ambition for discipline can manage this even for long periods of time. The next step down is to partially not eat solids. Anyone should be able to do this, especially for just a day.

Partial fasting means not eating “heavier” foods. In the vegetarian context, this means any grain (like rice or wheat) or bean.

This is considered the minimum discipline that can be called “fasting.” Honestly, it is hardly worthy of being called a discipline, since most people exploit the loophole to indulge in copious amounts of oils, sugars, and so on. But for a sincere person it is a true and excellent discipline.

Does “Sin Reside in Grains” on Ekadashi?

This is a way of saying “you should not eat” but saying it in a way that motivates people who don’t really think rationally, but think more with their feelings and instincts – who also tend to be the people incapable of practicing disciplines at more intense levels.

The simple logic is this:

Fasting is good = eating is bad.

Eating is bad = food is bad.

Food is bad = food has badness in it.

“badness” = “sin” (pāpā)