The Compendium of Bheḷa 3.3.2

3.3.2

alpaṃ laghvapi yaccānnaṃ bhuktaṃ duḥkhena jīryati | nāpnoti balavarṇau ca durbalāgniḥ sa ucyate ||

and food eaten, even if small in amount and light, digests with difficulty, / and he does not obtain strength and complexion: he is said to have a weak digestive fire.