Actually I do fine at work which help my coworkers not be worried when they see that I'm normal. During my last cleanse, I did feel weak/lazy/tired around day 3-4 then I went back to normal. I just slept more during those days, didn't work out, took it easy and that was it. Yeah, really I think the body has evolved to handle a food outage and have heard trouble only related to blood sugar/dizziness most of the time. People with health trouble may want to be monitored but other then that, I don't think it's a worry. Happy cleansing!