The Orthodox Church in India, along with the Syrians, Copts, and others observe this fast.
As to how they fast, it is all a question of economy. The traditional Nineveh Fast is as I said in my post above (it is different from the other fasts because of its length: only three days). But what can one safely do? The whole fast? Fasting until sundown? Or until three in the afternoon? As always, these questions are ones that the individual and his priest must deal with. We have the tradition, and it provides the guideline, but it can be tailored to suit our needs. The working generation, a pregnant lady, a sick fellow, a retired couple, children, etc. all have different needs, and have different capacities for such penance. So the fast is mitigated, more or less, depending on the person. And when one is used to doing a certain amount and then comes to a point where one must do less, I'm sure that in itself is a form of penance. I know that I'm used to a certain amount of fasting for now, but if I come to a point sometime in the future where I'll have to lessen it, I won't be happy about it since I'll feel like I'm "not doing enough" or as much as before, but at the same time, it is in obediently following the counsel of those in authority over me that real penance is done.