Charak Samhita
व्याधियुक्तस्य मन्दे तु सर्पिरेवाग्निदीपनम्। उपवासाच्च मन्देऽग्नौ यवागूभिः पिबेद्घृतम्॥२०८॥
If suppression of agni has taken place due to diseases than ghrita is best for agni deepana but if fasting is the causes of agni suppression than yavagu (gruel) along with ghrita should be taken.
english translation
vyAdhiyuktasya mande tu sarpirevAgnidIpanam। upavAsAcca mande'gnau yavAgUbhiH pibedghRtam॥208॥
hk transliteration by Sanscript