A deck of cards, two computer mice, some salad and two slivers of pie, please.

If you’re hoping to keep this Thanksgiving from 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 today 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? 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 — not a holiday that actually celebrates the act of eating.

So what’s the solution? Eat in moderation and set reasonable expectations.

Don’t try to starve yourself until dinnertime. Banking calories for the big meal leaves you famished and more likely to overeat, said Bonnie Taub-Dix, a dietitian and spokeswoman for the American Dietetic Assn.

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.

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

• Try eating a little of everything, even desserts, but just a few bites. Taub-Dix likes this approach because it lets people fully participate in the meal.
• 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 was an easy fix — use a smaller plate.