Astanga Hrudaya
गुरूणामर्धसौहित्यं लघूनां नातितृप्तता। मात्राप्रमाणं निर्दिष्टं सुखं यावद्विजीर्यति॥२॥
As a general rule, if the food is heavy to digest (such as oily food, non veg, sweets etc), it should be consumed till half of the satiation level is achieved. (Ardha Sauhitya). If the food is light to digest, it should be consumed till one is not overly satiated. (Na Ati Truptata). The right amount of food is that, which undergoes digestion easily
english translation
gurUNAmardhasauhityaM laghUnAM nAtitRptatA। mAtrApramANaM nirdiSTaM sukhaM yAvadvijIryati॥2॥
hk transliteration by Sanscript