Let me try the theory:

The very all-knowing, why the bread that is fresh, that is lying, if you eat it on the street always, ALWAYS so delicious? Just don’t rub about the house in the village, the fresh air, the sugar butt of a young neighbor who stands over beds on the morning landscape as an appetite stimulator. Even if in one hundred and sixteen floors to push your head into the window on the "fresh air" with a whirlwind in the teeth, the one immediately and the smell stunned, and the taste really becomes different.

Bread from ordinary white flour is a classic of fast carbohydrates. When used dramatically increases the level of glucose in the blood. This leads to the production of endorphin (hormone of pleasure), but for a full reaction requires increased oxygen intake, which is lacking in a suffocating room. I think that’s why picnics in nature are usually accompanied by increased appetite and good mood.