Who we eat with has a direct impact on how much we eat. For example, women tend to eat less when they dine with members of the opposite sex. And they eat even less when the man is attractive. People generally eat less in front of a stranger. Also they eat as much as they see other people eating. We also tend to consume more in a large group. Married couples eat healthier than singles do. And guys are big eaters when they are out with their make friends.
According to nutritionwonderland.com, women eat less to meet a societal expectation related to their appearance. Men eat more with other men to prove how macho they are.