I have always been curious about how emotions influence eating.

Events such as birthdays, weddings and landing a new job all call for a meal. On the opposing side - death, break ups and losing a job also call for some sort of a meal. Food is celebration, and food is comfort.

Is there a physiological connection or are these learned behaviors?

Short term stress, such as feeling nervous in a unsafe situation or the hours leading up to an important meeting can decrease intake. The brain produces corticotropin-releasing hormone, while at the same time the adrenals increase epinephrine production. Both mechanisms lead to a temporary suppressed appetite.

In contrast, long term stress leads to an elevation of cortisol. This hormone, released by the adrenal glands directly increases appetite for sweet & salty foods, and thus begins "emotional eating." Cortisol has also been shown to enhance motivation, including the motivation to eat.

Though there is a physiological component to stress eating, there is also a psychological aspect. Eating temporary relieves uncomfortable and negative feelings. This avoidance, or "numbing" only lasts as long as that bowl of ice cream does.

So... you can partly blame your hypothalamus for that third piece of pizza but stay aware of the drive to desensitize emotions. There are other options for comfort such as keeping a food/emotion diary, practicing meditation or yoga, talking with a friend or even just taking a ten minute walk. It is all about taking control.