A recent study has shown that eating out can encourage overeating or binging. Or perhaps those who do binge tend to visit restaurants more often...
The study (full PDF / abstract) compared food diaries of 117 women (46 who were "dieters" and 71 who had a history of binging).
"Both bingers and dieters consumed significantly more calories (226-253 kcal) and fat (10.4-16.0 gm) on restaurant days."
The Calories may not seem huge, but given that both groups were eating out approximately half of the days of the week (i.e. 3-4 times) -- then it does begin to make a difference.
The research also noted that:
"Women who binged more frequently were also more likely to eat out and experience difficulty with controlling their intake at restaurants."