Diet: Not What, But How Much

(CBS)  According to the USDA, Americans are consuming 150 more calories a day than they were 20 years ago. These extra calories are no small problem - over the course of a year, they can result in gaining 15 pounds.

To cut them from your diet, Fitness magazine diet and nutrition editor Leah McLaughlin suggests paying more attention to serving size.

"Lots of people are hung up on not eating fat or protein," she says. "But at the end of the day, Americans are just eating too many calories."

We are so used to being served thick, juicy burgers with piles of fries, giant salads loaded with dressing and towering desserts that most of us have no idea what the USDA even considers a reasonable serving.

Although there are several reasons for this, McLaughlin says it partly stems from consumers looking for a good deal.

"Americans expect value when they go out," she says. "When they're offered a lot more for only a small price increase, they ignore that they're also getting so many more calories."

There are some foods that we consistently overestimate portion size. The following are a few examples:

• Pasta - A serving of dry spaghetti is 2 oz. - The diameter of a quarter.
  
  
• Chicken or steak - A serving size is 2-3 oz. - The size of a deck of cards. Chickens are bred much larger today and one breast is often bigger than one serving.
  
  
• Peanut butter - A serving is 2 tablespoons - The size of an Oreo cookie. When you see a mother in a peanut butter commercial spreading the stuff on a sandwich, she's using closer to one quarter of a cup, McLaughlin says. That's 400 calories without the bread or jelly.

When buying pre-made or pre-packaged items, you usually can't choose your serving size. Bagels and muffins, two popular breakfast foods, are perfect examples of this.

Deli bagels or bagels from Dunkin' Donuts, for example, are monsters - they have one and half or two times more calories than the recommended portion, which should be about the size of a can of tuna fish.

Muffins also tend to be oversized. "Muffins should be the size of the ones you make at home," McLaughlin says. "But nobody does that anymore so nobody knows that that looks like!" Fitness magazine suggests that a one-serving muffin is about the same size as a tennis ball.

You may not be able to control the size of the bagel or muffin you buy, but that doesn't mean you have to eat the whole thing. McLaughlin suggests eating part of it for breakfast and saving the rest for a snack later in the day. This same practice should hold true in restaurants. When served a giant plate of food, ask to have part of it wrapped up. Or, ask whether you can order an appetizer-sized portion.

If you're unsure what an appropriate portion of a food should look like, Leah says, use your hand as a measurement. Meats should be the size of your palm; cereal or side dishes, the size of your fist, etc.

McLaughlin's final advice: use common sense and if you have a giant sandwich for lunch or lots of cheese and crackers before dinner, don't panic. Portions can balance themselves out over three or four days.

"If you overeat at one meal, compensate at another," she says. "It's all about balance."