My workouts fluctuate. Day 14 - I had SO much energy, that I took advantage of it and I never felt that overall tired feeling of working out. Rather, I just felt tired for each muscle that I trained (i.e. when it went in to muscle failure). Even at 11:00 at night I was still wired. The next day it wasn't the same scenario.
I just stepped up my workouts, swimming (laps - nothing hard core 10 laps 20 minutes) and I'm doing my 30/30 this month. I walk/run - starting for 10 minutes walking, running for 30 seconds and recovering to a walk and running another 30 seconds. The last five minutes of the 30 minute exercise, I just walk. I burn anywhere between 202 - 427 calories on that exercise, depending on my energy level. Swimming is another 100 cal, walking the dog also, 70 calories. I just don't want to fall below 1200 calories that are needed for body function (heart, lungs, liver, brain). I read the book and it's inconsistent in that it says 6-12 oz, but if you are getting hungry to have another glass of lemonade. So from that I'm concluding that's okay and my body seems to be telling me it needs more fuel.
Today was Day 20. I've drank my 12 drinks, but I still have to swim my laps and think I'll drink more lemonade tonight, I don't want to fall in to the trap of not consuming enough calories and my metabolism slows down.
Oh I'm 5'9.5" also and I'm trying to get down to 140.