A recent study showed that overweight people are more likely to have overweight friends. That makes sense in a "birds of a feather" kind of way.
We like to spend time with people who are like us. Similar people make us feel comfortable. A person with a weight problem may not enjoy hanging out with a thin person or a friend on a diet. The chubbier, nondieting friend may feel pressured to lose weight or be inhibited about enjoying certain foods.
As it turns out, not only does your diet influence which friends you pick, your friends influence your diet.
It can be a great joy to share food with friends. But when we dine with people we like, it's easy to lose track of how much we eat. In the excitement of conversation, we don't notice how many rolls we've eaten, if we're on our second serving — or perhaps third — of pasta.
Among friends, we also tend to eat for a longer period of time than when alone. We are having fun, and we want to hear or tell a funny story.
Eating is like shopping
Besides, it's just good manners to wait until everyone is done eating until we push off from the table . And eating is like shopping: the longer you stay at the mall, the more you buy. The longer you stay at the table, the more you tend to eat.
This tendency to chow down among friends is so strong that it is almost mathematically predictable, according to John de Castro, psychologist at Sam Houston State University in Huntsville, Texas.
On average, if you dine with one other person you will eat about 35 percent more than if you were alone. (Spouses don't have this effect because couples tend to get into a regular eating pattern and consume about the same amount.)
If you eat with a party of seven or more, you will gobble up 96 percent more, or nearly twice as much. Sound like Thanksgiving? And if you get a table for four, you will end up right in the middle, eating about 75 percent more calories than if you dined alone.
This may be one reason why close friends and family tend to weigh about the same. Some families are skinny and some families are not. If there are a majority of overweight people in a family, it is more difficult to lose weight because the frequency, quantity and time spent eating puts more pressure on the person who is trying to diet.
Enjoy alone time
But don't worry; this doesn't mean you have to choose between having friends and having a waistline. Just model yourself off of the right friends.
If you’re trying to lose weight, go to lunch with your Atkins-approved pals, not the group who usually ends up wolfing down pizza at midnight.
Also, sit next to slow eaters who can help you pace your eating, not the speed eaters who eat like they grew up in a family of 12.
And if you're going out to dinner with a few chums, follow the "rule of two." Limit yourself to two items in addition to the entrée. That could be a small appetizer and dessert, or two pieces of bread. But you can't have more than two.
If you follow these simple strategies, you won't feel deprived, you'll be less likely to overeat and you can still be popular.
Brian Wansink, Ph.D. is director of the Cornell Food and Brand Lab. His book "" has just been published in paperback.