Lay Buddhists observe the Full-moon day as a day of fasting when meals are not taken after mid day. On that day they abstain from sensual pleasures and the use of high and luxurious seats and beds. Time is spent on the practice of the Dhamma. This has to be developed as an inner strength.
Fasting alone does not lead to purification. The bhikkhus too fast daily between midday and the following dawn. But this is not called fasting. For some people when meditating fasting may work well, but for others it works just the opposite — the more they fast, the stronger their defilements get. It's not the case that when you starve the body you starve the defilements, because defilements don't come from the body. They come from the mind
There is the Dhammapada verse (with regards to ascetic Jambuka) in the scriptures that says that realization is far superior to mere fasting. It’s English translation is :
“Month after month a fool may eat only as much food as can be picked up on the tip of a kusa grass blade, but he is not worth a sixteenth part of those who have comprehended the Truth.”
But other ascetics at Buddha’s time did so. But it is said the prolonged, so-called meritorius fasting of other ascetics who have not destroyed the passions, is not worth the sixteenth part of a solitary day's fasting of an Ariya who has realized the four Noble Truths. There’s another Dhammapada verse (with regards to ascetic Bahu Bhandika) that says, that external penances such as fasting cannot purify a person.