A recent study conducted in three university dining halls found that women changed their food choices depending on the gender of their companions.
When eating one-on-one with a guy, the girls ate foods that contained significantly fewer calories than when eating with female companions. The study found a couple more examples of behavior worth noting that were published in the journal Appetite:
Overall, group size was not a significant predictor of calories, but women's calories were negatively predicted by numbers of men in the group, while the numbers of women in the group had a marginally significant positive impact on calorie estimates. Men's calorie totals were not affected by total numbers of men or women.
I found this fascinating and am wondering if you find these behaviors true for you.