Again, science tells us something we could have guessed on our own: our eating habits are dominated by our awareness and internalization of social norms. Or, to put it more simply, it's way easier to justify downing a 1600 calorie milkshake when all the cool kids are Instagramming it.
A recent report published by Frontiers in Psychology studied the interaction between the social relevance of portion size and food consumption. It turns out that we are more likely to consume bigger portions when we perceive this to be the norm.
It's pretty well established that people eat more when presented with larger portions. Think Levain cookies. They're mouthwatering, trendy, all over social media, and gigantic. These characteristics make it easy to down 500 calories while protesting but it's only one cookie.
What we eat has a lot to do with how appropriate we perceive the act of eating it is. This is where the influence of social norms come in. Binging on a massive plate of late-night nachos feels practically guilt free when out with your best friends. Suddenly, your late night drunchies are appropriate because people who are relevant to you (your friends) condone them. If they aren't relevant, you probably need new friends.
The interesting thing is that behavior by people you don't find relevant may have the opposite effect on how appropriate portion sizes seem. The research looked at the role of the "out-group" (i.e. socially irrelevant people) and "in-group" (i.e. socially relevant) on expected consumption. When people were made to believe that the "out-group" favored a larger portion size, they theoretically went for smaller portions. Meanwhile, when the "in-group" seemed to go for a larger portion size, they opted for larger portions.
We're less upset than you'd think. If overeating is inevitable with people we like, indulging isn't the worst thing in the world. While the research shows that our foodie-centric weekend trip to Smorgasburg may not go over well with our summer body goals, we'll pretend we didn't know.