The Associated Press

What happens when you combine Thanksgiving — a holiday dedicated to overindulging — with America’s love of all things Supersized? Not as much as you’d think.

While Americans are notorious for cranking up the calories and portions compared to a generation or so ago, small changes in the nation’s diet seem to have buffered Thanksgiving dinner from some — but not all — of our bigger-better mentality.

To find out just what has changed about America’s official gut-busting dinner, The Associated Press asked Cornell University’s Food and Brand Lab to analyze recipes from the 1950s and compare them to contemporary versions.

Previous studies of non-Thanksgiving recipes by lab director Brian Wansink had found that calorie counts for many classic cookbook recipes have ballooned by nearly 40 percent during the past 70 years.

But Thanksgiving staples didn’t follow that trend.

Calorie counts for five of the eight recipes tested actually dropped by almost a third when comparing 1956 Better Homes and Gardens recipes to the 2006 edition of the “Better Homes and Gardens New Cookbook,” changes Wansink attributed partly to the use of lower-calorie ingredients, such as low-fat milk instead of cream. Surprisingly, some serving sizes went down over the decades too.

Per-serving calorie counts dropped an average of 102 calories for green beans with almonds, stuffing, mashed potatoes, candied sweet potatoes and pumpkin pie. They went up 26 calories for rolls and were essentially unchanged for corn and candied carrots.

That puts the total calorie count for a contemporary Thanksgiving dinner of those eight fixings, plus a turkey drumstick, at 2,057 calories.

The tally for 1956 was 2,539, according to Cornell researcher Laura Smith.

But those numbers are accurate only if you eat proper serving sizes. And when was the last time you carefully measured out 6 ounces of candied sweet potatoes or called it a day after just one roll? Especially on Thanksgiving.

Wansink’s research repeatedly has shown that controlling portions is not something Americans today are skilled at.

“There might be a little less butter put in the dressing or there might be fewer marshmallows on the sweet potatoes,” he says. “But where you end up messing with them, you end up serving up a lot more than your grandfather served himself.”

Meals served at home have followed the same trend as restaurant and packaged food portions — more, more, more.

Even the plates on which Thanksgiving is served have grown since a generation ago (by more than a third according to Wansink’s studies). By today’s sensibilities, older china sets seem more fitting for tapas than Turkey Day.

And Wansink’s research has shown a link between larger plates and larger portions. Put simply, a little lump of mashed potatoes can look awfully lonely on a foot-wide plate. The same dynamic works with wine consumption. Today’s bigger glasses get bigger pours.

Wansink added that even in cases where recipes are about the same size, today’s families are smaller. That means more per person.

Even the turkeys are bigger. Today’s big-breasted birds on average are 10 pounds heavier at slaughter compared to 1950, according to federal data. Recipes from the ’50s actually included roasting instructions for 5-pound birds. Good luck finding one that small today.

Joan Salge Blake, a nutrition professor at Boston University and spokeswoman for the American Dietetic Association, thinks the tradition-bound nature of the Thanksgiving meal probably played a role in keeping the recipe calorie counts down.

“These are Grandma’s recipes,” which are less likely to change over generations, she says.

Nancy Hopkins, deputy editor of food and entertaining for Better Homes and Gardens, isn’t surprised by Wansink’s findings. She says her company has responded to consumers who increasingly ask for healthier options, including for Thanksgiving.

To see a real calorie spike, all you have to do is compare Thanksgiving today to 1621, the year of the feast that inspired the holiday.

The menu enjoyed by the settlers and their Wampanoag guests — commonly knows now as the Pilgrims and Indians — is lost to history. But the limited clues available point to tables loaded with venison and wildfowl, according to Kathleen Wall, colonial foodways culinarian at Plimoth Plantation at Plymouth, Mass. Other dishes may have included lobster, mussels, boiled greens and pumpkins.

But forget the fancy sides.

The Pilgrims probably had no potatoes in 1621, and if they had butter and sugar, it came over on the Mayflower the year before. There was no dough, so no pies. They may have eaten cranberries, but not as a sweetened sauce. The birds probably were stuffed with little more than quartered onions and parsley, Wall said.

The likely calorie count? A settler who gave thanks with a turkey drumstick, some lobster, boiled spinach and stewed pumpkin washed down by water — sorry, no beer or wine yet — probably only ingested about 550 calories.

No fancy, fatty stuff for the settlers who came over on the Mayflower. Salge jokes “they would have sunk the ship.”