I don't have any hard evidence to back what I am saying, just my own experiences, but it seems logical that in a time of physical stress and recovery that your body is going to need energy to go through that process and that the more you give it then potentially the faster it might do that.
Like I say just assumptions but it works for me, detoxes where I haven't eaten properly have stretched on forever. I did one where I got a vomiting bug after about a week and I couldn't keep any fluids let alone food down. I was at the point where I should have been basically ok but I just felt fucked for like a whole other week after the first barely eating because I felt ill and feeling terrible and totally fatigued. I smoked a joint which removed the nausea and I and got the munchies, ate a shit load of food, did the same again in the morning and I was basically fine from there.
I honestly think people underestimate the importance of calories, if you go five days or a week with barely eating anything (like many do when detoxing) then you're going to feel like shit whether you're going through a detox or not. The body needs calories, it can't magic recovery up out of nothing.