Gluttony is not a common vice for me, but it is an annual obligation.
If I don't stuff myself on Thanksgiving to rival the turkey, I am sure to hurt my mother's feelings. We can't have that! So stuff I do -- until able to stuff no more.
And once I have bravely soldiered up to that line, I lay down my fork. And then I, or one of my comparably sated tablemates, is the first to say something like: "Whoa! I am so full, I couldn't eat another bite!"
The aroma of pumpkin pie, pecan pie and chocolate brownies wafts in from the kitchen, so we are quick to append: "What's for dessert?"
There is usually some savant among the holiday guests who notes that of course there's room for dessert -- there is a hollow leg or extra stomach set aside for just that purpose.
But as you likely know, we take anatomy in medical school, and explore all the nooks and crannies of the human body. I have it on good authority that the proverbial extra stomach, or hollow leg, has never been found. My cadaver certainly had neither.
But the fact is, we do have room for dessert when stuffed to the gills (which anatomy lab has also failed to find, by the way). How can that be?
It is courtesy not of the stomach or the leg, but of the brain, and specifically the appetite center housed in the hypothalamus. The explanation is sensory specific satiety.
Stuffed, Yet Insatiable
Translated into English, sensory specific satiety means, basically, feeling full of one kind of food but not necessarily another. The appetite center is stimulated by several different flavor categories, among them salty, savory and sweet.
When you eat enough of something that is salty and crunchy, salty and crunchy loses its appeal. But the appetite response to luscious and sweet is just waiting to get switched on. Go from salty and crunchy to sweet and luscious, and you turn on a whole new appetite response. When satiety, or fullness, is reached for one taste category, appetite remains for the others.
This is why we can be full at the end of a meal and still have room for dessert. We are, indeed, full -- of salty, and savory and meaty. But the appetite center for sweet hasn't even gotten into the game yet.
And research suggests that the "satiety threshold" for sweet -- how many calories in that category it takes to register full -- is set higher than for other flavors. So it's no coincidence that almost every culture ends a meal with dessert, rather than starting with it.
You've experienced sensory specific satiety whenever you felt full at the end of a large meal, but still had room for dessert. You've also run into it when, despite your vow not to do so, you overate at an all-you-can-eat buffet.
Variety is the spice of life, we say, and it certainly spices up the appetite center.
'Hidden' Variety Makes Foods Irresistible
But more problematic than the obvious variety built into the occasional feast or buffet is the hidden variety engineered into processed foods.
Most processed foods have long ingredient lists that include various forms of sugar, notably high fructose corn syrup; various forms of sodium, such as monosodium glutamate; and artificial flavorants as well. And the flavors hidden in foods can be quite surprising.
Many popular breakfast cereals, for instance, are more concentrated sources of sodium than potato or corn chips. Many popular pasta sauces and salad dressings are more concentrated sources of sugar than ice cream topping.
That variety puts our appetite center into overdrive on Thanksgiving would not be a problem, if the highly processed modern food supply weren't already doing the same thing the other 364 days of the year! Remember the "Betcha' can't eat just one!" ad? They weren't kidding!
The net effect of all this appetite stimulation is that it takes more total eating to feel full, and leaves us all with a simple, unpleasant choice: be heavy, or be hungry.
Tips to Beat the 'Hollow Leg' Phenomenon
But you can opt out altogether by using some skill power to create a third choice: filling up on fewer calories. Here's a short list of tips for turning sensory specific satiety from adversary to ally:
Base your diet predominantly on simple, natural foods such as fruits, vegetables and whole grain products.
Restrict the variety of foods and flavors consumed during any given snack, meal or day to a moderate level.
Select foods in various categories (e.g., snack foods, cereals, baked goods, sauces, etc.) that are limited in the number and variety of ingredients; favor simple over highly processed foods.
Avoid letting dessert be a reward for eating a larger rather than a smaller meal.
Avoid buffets and buffet-style eating.
Limit evening snacking to only one type of food, or avoid it entirely.
Determine the timing and options for dessert in advance rather than when faced with tempting choices.
Limit the variety of foods kept in the house at any given time.
Indulge the occasional craving.
As for the holiday, make your indulgence more about quality, than quantity. Whatever your personal, traditional favorites -- from turkey with gravy to tiramisu -- by all means enjoy those. But forgo the more mundane items you can have any time that tend to come along, such as chips, crackers, and cheese. A one ounce slice of gouda cheese adds 100 calories; five Ritz crackers add another 100.
Just because something is sitting out in a bowl or on a platter does not mean you have to eat it.
Avoid an excessive variety of choices. Look over the entire buffet, and identify those items that interest you most. Limit the variety of foods you put on your plate at any one time. Just as a shopping list prevents a trip to the supermarket from wandering off course, a few minutes to plan your approach to the buffet table will maximize the ratio of pleasure to calories. Choose wisely.
Of course, the best advice for Thanksgiving is just to give in, and live it up! It's a holiday after all. Make prudent diet choices all year long, and you can do just that on the holidays with no harm done.
We do know why there is always room for dessert, and that knowledge can help you master your appetite. Some insight into your hypothalamus can help you do what folklore about nonexistent hollow legs cannot: fill up on fewer calories! I apply this knowledge to good effect every day.
But for whatever it's worth, I intend to stuff myself on Thanksgiving!
Dr. David Katz is director of the Prevention Research Center at the Yale University School of Medicine and medical contributor to ABC News. His book, Dr. David Katz's Flavor-Full Diet explores further the connection between satiety and weight control.
Visit Dr. Katz's Web site at www.davidkatzmd.com.