It is unclear if caffeine breaks a fast by stopping autophagy or other metabolic processes, or if there is a crosstalk between caffeine receptors and glucagon receptors.

“Not sure how much the effect I’m looking for is attenuated with it tho since we can’t actually measure what matters most.”

“Because that's how we are feeling the effect of coffee in the rest our body, because the stomach started working, it absorbed coffee, it sent it to liver, liver might have metabolized it slightly and started to send it to the rest of the brain and body. And then it gets back to kidney, it gets metabolized and excreted. So then the question is, forget about circadian clock, now if we think about just metabolism and, say, mitochondria function, or even, say, go back to autophagy, and then ask, "Is caffeine breaking the fasting so that it stops autophagy, or it stops something else? Or is there a crosstalk between, say, caffeine receptor and glucagon receptor so that it does?"”