Working makes me hungry

I started off the morning 250.4 pounds and headed to work for a 13 hour work day.  I ate a turkey sausage breakfast sandwich for lunch and leftover chicken and dumplings with some very good veggies for lunch.  My problem was I starved all day long.  I have no idea why but I could not get full I finally bought a candy bar (even though I really did not want it and it didn't even start to fill me up.  This was not a mental hunger I was genuinely hungry and have no idea why.  When I got off work I ran by McDonald's and ordered a double burger without cheese a small fry.  So much for eating healthy but tonight's weight upon arriving home was only 252.  Not sure what kicked my metabolism in but something did.  It maybe that I walk continuously for 12 hours straight at work. I am really curious how far we walk a day (one of the nurses heard it equaled about 5 miles a day)  back at it tomorrow and hopefully better snacks and a better plan.