Do you ever feel like Goldilocks? "Is this bowl of porridge too small? Is it too big? Or is it just right?"

One of the primary reasons so many people are overweight is lack of portion control. Food advertising is the biggest culprit. You can Supersize for only one additional dollar. Buy two candy bars for the price of one. And don't even bother trying to find a "small" serving of most foods; they've morphed into ever-expanding sizes.

Why do portions matter anyway?

One word: calories. A small pear contains 60 calories, a large pear has 80. A small serving of fries at McDonald's has 220 calories, while a large serving has 400 calories. If you eat large fries three times each week for a year, that's an additional 8 pounds of fat you're packing on your body. Ultimately, losing weight comes down to calories.

How portion savvy are you?

Try this quiz to see how much you know about standard serving sizes:

1. A serving of fruit juice is:
a) 4 fluid ounces
b) 6 fluid ounces
c) 1 cup

Answer: According to the food pyramid, a serving is 6 fluid ounces, or 3/4 cup. If you're used to Weight Watchers or other exchange-type programs, 1/2 cup is a serving. Or you could read the label, but remember that individual-size bottles of fruit juices and drinks such as Snapple have grown over the past few years; one "individual" bottle usually serves 2 1/2.