Once when the Buddha was living at Savatthi, King Pasenadi of Kosala ate a whole bucketful of food, and then approached the Buddha, engorged and panting, and sat down to one side. The Buddha, discerning that King Pasenadi was engorged and panting, took the occasion to utter this verse:

"When a person is constantly mindful,
And knows when enough food has been taken,
All their afflictions become more slender
They age more gradually, protecting their lives."

Now at that time the brahman youth Sudassana was standing nearby, and King Pasenadi of Kosala addressed him: "Come now, my dear Sudassana, and having thoroughly mastered this verse in the presence of the Buddha, recite it whenever food is brought to me. And I will set up for you a permanent offering of a hundred kahaapanas every day."

"So be it, your majesty," the brahman youth Sudassana replied to the king.

Then King Pasenadi of Kosala gradually settled down to [eating] no more than a cup-full of rice. At a later time, when his body had become quite slim, King Pasenadi stroked his limbs with his hand and took the occasion to utter this utterance:

"Indeed the Buddha has shown me
Compassion in two different ways:
For my welfare right here and now, and also for in the future."

Donapaka Sutta - King Pasenadi Goes on a Diet
Translated from the Pali by Andrew Olendzki
http://www.zhaxizhuoma.net/DHARMA/Tripitaka/DonapakaSutta.htm