A deck of cards, two computer mice, some salad and two slivers of pie, please. If you're hoping to keep this Thanksgiving from (search) turning into another gut-busting affair, that's what your plate should look like: a serving of turkey no larger than a deck of playing cards and half a cup each of two starches. (A half-cup is about the size of a computer mouse.)

And that's being generous.

But Americans generally are clueless when it comes to proper portions, and on Thursday most will belly up instead to platters piled high with more calories and fat than an average person should eat all day.

So how do you celebrate the harvest bounty without blowing your diet (search)? Start by understanding the problem.

Portion distortion started as a fast-food phenomenon, but during the past 20 years, meals at home have grown just as inflated, said Barry Popkin, a nutrition professor at the University of North Carolina at Chapel Hill.

Americans are eating about 200 more calories per day than they did during the 1970s. And that's a normal day. Now add a holiday that not only is celebrated by eating, but actually celebrates the act of eating.

To see how easy it is to overdo it, assume you eat the correct portions of the Thanksgiving staples — turkey, mashed potatoes, cranberry sauce, stuffing, gravy, a vegetable, two rolls, a glass of wine and a dessert.

According to the American Dietetic Association (search), that is still nearly 1,500 calories — almost enough for a typical woman for a day. For perspective, it takes only an extra 10 calories a day for a person to gain a pound of fat a year.

So what's the solution? Eat in moderation and set reasonable expectations. Hey, no one said it would be easy.

Start by not starving yourself the rest of the day. Banking calories for the big meal leaves you famished and more likely to overeat, said Bonnie Taub-Dix, a dietitian and spokeswoman for the dietetic association.

In fact, eat a healthy snack — such as vegetables with lowfat dip — before the meal so you eat less of the heftier items.

For the meal itself, aim for about 3 1/2 ounces of protein (the size of a deck of cards) and 1 cup of starches (about two computer mice). That should fill half the plate. The rest should be vegetables.

Here's where the math gets tricky. Those cheese cubes you snacked on before the meal count toward your protein. That means less turkey, so choose wisely.

Same for the starches. Want mashed potatoes, stuffing and a roll? Can you fit it all in a cup? Don't forget, the pie crust and crackers that came with the cheese count in this category, too.

Taub-Dix suggests several approaches. Use the one most likely to leave you satisfied.

_ Try eating a little of everything, but that means just a few bites. Taub-Dix likes this approach because it lets people fully participate in the meal and doesn't leave them feeling deprived. This goes for the multiple desserts, too.

_ Eat only the unique foods. Mashed potatoes and turkey may be traditional, but they also are easily had any day of the week. Instead, use those calories for stuffing, cranberry sauce, pumpkin pie and other more seasonal items.

_ Fill up on salad and vegetables before heading for the turkey and candied sweet potatoes. Then if you are still hungry, hit the vegetables again after the turkey to reduce the amount of dessert you eat.

_ Visualize your stomach; it's about the size of two fists. If the food on your plate won't fit, cut back.

Speaking of visualization, for many people part of the joy of Thanksgiving is a plate piled high with goodies. Dee Sandquist, another ADA dietitian, said that is an easy fix — use a smaller plate.

Not so easy is the cleaning up. Remember that every bite counts, so if you plan to nibble as you wrap leftovers, leave room for those snacks while you're still at the table.

The good news is that no matter what, you are likely to overeat. Give yourself permission ahead of time.

"Thanksgiving isn't the time to cut back, but there are plenty of people who literally feel sick after Thanksgiving," Taub-Dix said. "You want to try to have as good a time as you can enjoying the foods you haven't had in a while, but in a way that lets you walk away from the table feeling good."

A little moderation may mean not feeling guilty — or the need to unbutton your pants at the end of the meal.