I read somewhere that you can totally stop eating for weeks at a time.
Not that I would ever want to try that.
I was hospitalized following an accident many years ago. The hospital starved me for four days. I was so hungry that I was begging for food... all they gave me was Jello.
At the time, there were no CAT or PET or MRI scans; the only way to determine if I had internal injuries was to wait and see if I would develop symptoms. The fact that I became hungry was an indicator that I had no internal injuries.
It was not a nice experience.