There was a time when the Persian King Bimbisara of Rajagaha ate a lot of food every day, and he became very fat. Even a little exercise would make him sweat profusely. One day, after finishing his meal, he went to visit Buddha at his residence and paid his respects before sitting down.

At that moment, Buddha saw the sweating and panting king wiping off the sweat from his head and body with a towel. He said to him, "Your Majesty, wise people often generate right mindfulness in their hearts. They know how to control their daily food intake and avoid overeating. A balanced diet can reduce various illnesses' invasion on your body and alleviate suffering caused by them. By controlling your daily food intake wisely, you can slow down aging and prolong your life."

Then Buddha recited this verse:

"By always holding right mindfulness,

And knowing how much food is enough,

One will suffer less,

Age slowly but live long."

After hearing Buddha's teaching, King Bimbisara turned around to Ananda who stood behind him saying,"Ananda! From now on whenever I eat my meals each day; you should recite this verse of the Blessed One beside me; I will reward you with one hundred coins per day for doing so." 

Ananda respectfully replied," Your Majesty! I shall obey your command." So Ananda memorized Buddha's verse which he then recited beside King Bimbisara during meals:

"By always holding right mindfulness,

 And knowing how much food is enough,

 One will suffer less,

 Age slowly but live long."

Once King Bimbisara heard this verse repeatedly during meals gradually reduced his amount of food intake. After some time passed by; His excess weight began decreasing while firm muscles started showing up all over his body instead.

King Bimbisara was very pleased with his strong and healthy body. He danced with a sword in the royal garden, saying joyfully," The Blessed One's compassionate teaching has truly benefited me now and in the future!" 

Pali original scripture

SN.3.13/(3). Doṇapākasuttaṃ

　　 124 . Sāvatthinidānaṃ. Tena kho pana samayena rājā pasenadi kosalo doṇapākakuraṃ bhuñjati. Atha kho rājā pasenadi kosalo bhuttāvī mahassāsī yena bhagavā tenupasaṅkami; upasaṅkamitvā bhagavantaṃ abhivādetvā ekamantaṃ nisīdi.

　　 Atha kho bhagavā rājānaṃ pasenadiṃ kosalaṃ bhuttāviṃ mahassāsiṃ viditvā tāyaṃ velāyaṃ imaṃ gāthaṃ abhāsi–

　　 “Manujassa sadā satīmato, mattaṃ jānato laddhabhojane.

　　 Tanukassa bhavanti vedanā, saṇikaṃ jīrati āyupālayan”ti.

　　 Tena kho pana samayena sudassano māṇavo rañño pasenadissa kosalassa piṭṭhito ṭhito hoti. Atha kho rājā pasenadi kosalo sudassanaṃ māṇavaṃ āmantesi– “ehi tvaṃ, tāta sudassana, bhagavato santike imaṃ gāthaṃ pariyāpuṇitvā mama bhattābhihāre (bhattābhihāre) bhāsa. Ahañca te devasikaṃ kahāpaṇasataṃ (kahāpaṇasataṃ) niccaṃ bhikkhaṃ pavattayissāmī”ti. “Evaṃ devā”ti kho sudassano māṇavo rañño pasenadissa kosalassa paṭissutvā bhagavato santike imaṃ gāthaṃ pariyāpuṇitvā rañño pasenadissa kosalassa bhattābhihāre sudaṃ bhāsati–

　　 “Manujassa sadā satīmato, mattaṃ jānato laddhabhojane.

　　 Tanukassa bhavanti vedanā, saṇikaṃ jīrati āyupālayan”ti.

　　 Atha kho rājā pasenadi kosalo anupubbena nāḷikodanaparamatāya saṇṭhāsi. Atha kho rājā pasenadi kosalo aparena samayena susallikhitagatto pāṇinā gattāni anumajjanto tāyaṃ velāyaṃ imaṃ udānaṃ udānesi– “ubhayena vata maṃ so bhagavā atthena anukampi– diṭṭhadhammikena ceva atthena samparāyikena cā”ti.