Snacking used to be a no-no. Three squares a day will satisfy you just fine, the common thinking went, while eating between meals will ruin your appetite for the scheduled ones.

But snacking has become a way of life. Americans opt for a sugary doughnut for a lift in midmorning. They grab a candy bar or a bag of potato chips from the vending machine when the stomach starts growling around 4 p.m.

Too often, those chips, cookies and candy bars provide nothing but empty calories, which are stored as fat. The wrong snacks can sabotage the most well-planned diet.

If you down two soft drinks and nibble a candy bar every day, eliminating these nutritional extras can mean a one-pound weight loss in a week, says Nancy Rodriguez, a registered dietitian and associate professor of nutritional sciences at the University of Connecticut.

There is another benefit to choosing snacks with fewer calories and more nutritional punch. "If you commit to make a lifestyle change to lose 200 to 300 calories a day, then it is easier to keep off the weight because you've made a change in habits," Rodriguez says.

Most Americans fall short of the minimum two-servings-a-day recommendation for fruit, the federal Agricultural Research Service found in its most recent survey of American eating habits. Vegetable eating ranked slightly higher: The typical American eats the minimum three servings a day. But we can't pat ourselves on the back quite yet. Potatoes, especially in mashed and French-fried form, account for almost half of those vegetable selections.

So remember when choosing snacks to make label-reading a habit, especially to check fat and sugar content. Total fat calories should not exceed 30 percent of the food's total calories. And keep in mind that snacks that are labeled "no cholesterol" may still be high in other fats.