The 2-Minute Thought: The Calendar Effect and Eating

In a recent Financial Times story that profiled several workers making sandwiches at the UK-based sandwich shop Pret A Manger, it was fascinating to read about the rhythms of the shift from 5 am through the breakfast and lunch rush. 

It also was fascinating to read that there’s a weekly pattern to what customers choose to eat

According to Pret’s software, sales of soups, salads, and fruits peak on Monday, then decline over the course of the week.  Sales of comforting desserts and cakes peak on Thursdays.  Then croissants, bacon, and breakfast sandwiches peak on Fridays. 

Perhaps this little piece of information is neither here nor there, but it’s hard not to wonder if there aren’t behavioral anomalies here similar to those in other spheres of life.  For one thing, is there a calendar effect in our eating?  What is it that makes our eating behavior differ on different days of the week?

Can it be that we start the week with good intentions and then break down as the week progresses?  Or perhaps it is that by Thursday and Friday, we already are preparing for the weekend, when we generally consume more calories than during the work week.

A study published by the National Institutes of Health in 2014 tracked weekly weight changes in 80 men and women and found that a person’s minimum weight was most often observed on Friday, while a person’s maximum weight was most often observed on Sunday or Monday.   Perhaps that is why people look so forward to getting a healthy start on Monday.

And then it’s also possible that just as we do “mental accounting” with money, we do it with eating too.  Mental accounting is when we don’t treat all of our money as one big pool, but divide it up into separate mental accounts according to purpose or source.  That means we can see it as a splurge to take a $20 taxi ride instead of the subway, and yet view $20 spent on two movie tickets as perfectly reasonable.  We keep the $20 for transport and the $20 for entertainment in different mental buckets.  But in the end, $20 is $20 is $20.

Likewise, we seem to cordon off different days into different categories when it comes to eating.  Somehow, the rules for weekday eating go out the window on the weekend.  And holidays?  Holidays are just a lost cause, a wholly different category of indulgence.  But weight gain happens whether overindulgence occurs on a weekday or a weekend.  Your body couldn’t care less if it’s a Saturday or Christmas. 

And to top it all off, we tend to mentally “frame” our eating into days or 24-hour periods.  We count calories by the day, and nutritional standards make daily intake recommendations.  We think of each day as a fresh start.  But most food and nutrition experts will tell you that what really matters is consistency in eating patterns over long periods of time. 

Have you ever heard that if you want to lose weight, you should eat breakfast, and that if you eat breakfast already, you should try eating the same breakfast for multiple days a week?  That’s because repeating the same meals can help you shed pounds.  Somehow, repeating meals inhibits the tendency to bucket days and meals into different categories with different rules.

And for a final piece of trivia, Pret A Manger knows that December 15 is the annual peak of its sales of bacon baguettes and breakfast sandwiches.  Is that random?  Is it because of the season?  The colder weather?  Or is it the beginning of the shift into holiday mode?


Please note: The 2-Minute Thought will be off next week and will return January 18.