This is just my anecdotal evidence. I can not feel good at that times when I do not work in the office (my non-office job is welding which is sometimes better to perform not in building to prevent breathing with chemicals). I tried a lot of really strange things like consume more than 1kg of sugar per day or to drink a sunflower oil to get rid of hunger quickly, but nothing can replace meat for me, especially in cold part of year, which in my home has already started. Either I eat meat at least 2 times per day or I feel hungry and perform a poor quantity of results.