The science behind why I (and maybe you) ate too much for Thanksgiving

So, you know how all sorts of products we use are always trying to manipulate us by recording out “streaks,” etc.  Well, I really should not care at all, but, I am, apparently on a 49 day streak of posting here.  So damnit, I’m going to keep my streak going.  I was about to set this aside for quick hits this weekend as I spent the day just really enjoying Thanksgiving with family (so great to hang with my sister-in-law’s family all day), but, the streak!  And, it’s pretty damn interesting. And, I still feel full!  (In complete keeping with the article, I could not resist the pecan pie even though I was already full)  So, science via the NYT health newsletter:

One of the more curious phenomena of the Thanksgiving meal is how we can feel completely full, yet somehow always find room for dessert.

Our ability to eat a ridiculous amount of food on Thanksgiving Day is related to the sheer variety of foods typically offered on a holiday table. Variety excites the appetite.

This “variety effect” is an evolutionary adaptation that served us well during pre-buffet times. Imagine if your ancestors binged on buffalo meat and then stumbled across a patch of ripe berries — but everyone was too full to eat them. Skipping dessert in that scenario would mean missing out on a stash of important nutrients. (And if that had happened, you probably wouldn’t be reading this now.)

The mechanism that allows us to make room for dessert is called sensory specific satiety, which means that the body has different limits for different foods as a way to help ensure a balanced intake of nutrients. Barbara Rolls, a professor and the director of the Laboratory for the Study of Human Ingestive Behavior at Pennsylvania State University, has been studying sensory specific satiety since the early 1980s.

“It’s the reason most of us manage to eat a balanced diet even if we don’t have nutritional knowledge,” Dr. Rolls said. “Variety is our friend in terms of nutritional balance.”

Over the years, Dr. Rolls has asked countless adults and children to fill up on savory foods like chicken or sausages. When offered a second serving, study subjects were often too full to eat much more. But when they were then presented with cookies, bananas or raisins, they always had room for another bite.

“It’s a change in your hedonic response to the food you’ve just eaten,” said Dr. Rolls, referring to the pleasure we get from eating. “If you’ve had a lot of salty and savory foods, the sweet foods might get more pleasant.”

Fast-forward to the modern Thanksgiving table, and you begin to understand why, on the fourth Thursday of November, so many of us become eating machines. After filling up on a few rounds of turkey, mashed potatoes and stuffing, chances are you’ll feel quite full. But when the pumpkin pie with whipped cream comes around, your brain will sense an entirely different kind of food, and suddenly, you’ll find yourself reaching for pie.

But don’t worry. While sensory specific satiety allows you to keep eating new foods, eventually your body will tell you to stop eating. After about 1,500 calories in one sitting, the gut releases a hormone that causes nausea.

Notably, the satiety signal is particularly strong in children and diminishes with age. In studies by Dr. Rolls, children were allowed to eat unlimited quantities of M&Ms. But once they were full, they had a strong response to being offered more. “These little kids said, ‘These taste yucky — I don’t like them anymore,.’” Dr. Rolls said. “We’d never seen as strong a response in adult subjects.”

The reason for the pronounced difference in response by age isn’t clear, Dr. Rolls said. It may have to do with a natural decline in sense of smell and appetite as we get older. Or it could be that a lifetime of eating highly processed foods interferes with our natural satiety signals.

Pretty fascinating, honestly.  I suspect I’ll be using that 1500 calories factoid in the future.  Not to mention the phrase, sensory specific satiety.  

Hope everybody had a great Thanksgiving!

About Steve Greene
Professor of Political Science at NC State

One Response to The science behind why I (and maybe you) ate too much for Thanksgiving

  1. R. Jenrette says:

    There is also a lot of social pressure going on. Our culture says its OK and people are expected to pig out on Thanksgiving. It’s like a Bacchanalia was to the Romans – feast time.
    Don’t forget to set your scale back 15 pounds the night before Thanksgiving!

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