Most of us already know we should be cutting back on the portions of food we eat and have heard that restaurant meals contain much more than we need. But few of us have a good sense of portion sizes or know that popular packaged foods mostly are not single servings.

Seton Northwest clinical dietitian Janessa Slatky, RD, LD has some ideas to help us apply portion control.

"Over the past 20 years, portion sizes haven't just doubled," believes Janessa. "In fact fast-food restaurants are now serving up portions that are two-to-five times larger than they used to be, while ready-to-eat and prepared foods can be two-to-eight times larger than what the USDA defines as a serving size. This means your morning muffin may actually serve eight people!"

Why so much confusion?

"With 65% of American adults over age 20 overweight, restaurants and grocery stores that serve or sell larger portion sizes may carry some of the blame," answers Janessa. "For instance, the USDA guidelines set the serving size for cooked pasta at 1/2 cup. A typical restaurant portion of pasta is about three cups. Here's where even a Registered Dietitian can get confused- the Nutrition Facts Label on a bag of pasta (governed by the Food and Drug Administration) states a serving size of cooked pasta as one cup. It's no wonder there's so much confusion about what a serving should be. There is little consistency between food labels, government recommendations, and restaurant servings."

Take Charge of Your Portions

The bottom line is that it's up to you to manage portion sizes. Janessa has some tips to help you be in charge of your portions.

• First you need to know how much food (in calories) you should be eating. This is determined on factors such as height, weight, age, sex, health status, and physical activity. The USDA's MyPyramid plan has a convenient calculator to estimate how many calories you need each day. Rule of thumb: if you're gaining weight, you are taking in more calories than you are burning.
• Look at the serving size on the Nutrition Facts Label to help determine portion size. Many people don't know that a microwave burrito, or a pack of Ramen Noodles actually contains two servings. Most of us eat the entire package and end up with double the calories.
• Notice the calories that you're drinking. A 20 oz soft drink is labeled as 2 1/2 servings. That's 250 calories for the entire soda, not just 100 calories listed on the label.
• Restaurant entrees are rarely the correct portion size and many are big enough to share with two or three people or save for another meal. Divide your meal and have it bagged before you start eating if you know you'll be tempted to clean your plate. Consider ordering a half-sized portion, or order off of the children's or senior citizen's menu.
• Learn to eyeball a serving size. Measure food you eat at home to see what a serving size looks like on a plate. This will help you determine a reasonable portion size when eating out.
• Don't eat right out of the bag. Measure out a portion size into a bowl and put the bag away. Our tendency is to eat until the bag is empty.
• Avoid super-sizing!!

Convenient Portion Size Estimations

If you are eating on the run, it's not convenient to measure your food. Janessa suggests some everyday size measures to help you estimate portion sizes.

• A serving of meat is 3 oz and looks like a deck of cards.
• A serving size of Peanut Butter is 2 oz and looks like a ping pong ball.
• A serving size of fruit should look like a baseball; keep in mind a banana has 2 servings.
• A serving of cooked vegetables should look like a light bulb; a little larger if the vegetables are uncooked.
• An ounce of cheese looks like the tip of your thumb.
• Salad dressing or mayonnaise should look like a ping pong ball.
• A teaspoon of butter or margarine is about the size of a postage stamp.

Portion Distortion Quiz

As part of its Fit Nation Special Report, CNN recently ran an interesting quiz on portion distortion that let's you test your knowledge of portion growth.