If you realize that you are eating because you are feeling stressed out, allowing yourself a few minutes to take a deep breath can break the cycle of overeating.
"rapid breathing is controlled by the sympathetic nervous system. It's part of the "fight or flight" response — the part activated by stress.
In contrast, slow, deep breathing actually stimulates the opposing parasympathetic reaction — the one that calms us down"
http://www.npr.org/2010/12/06/131734718/just-breathe-body-has-a-built-in-stress-reliever&sc=fb&cc=fp