When parents opt for convenience and take kids to fast-food restaurants, they're feeding them foods that account for almost half a child's daily caloric intake and up to 100 percent of their recommended daily sodium levels.

In a study published in this week's journal of Childhood and Obesity, researchers out of the University of California San Diego found that lunchtime meals at fast-food restaurants accounted for between 36 to 51 percent of a child's daily caloric needs.

Furthermore, 35 to 39 percent of calories came from fat and the meals provided more than 50 percent of the recommended total daily sodium intake for most children.

For preschoolers, however, that daily intake shot up to as high as 100 percent.

The study was meant to evaluate the nutritional content and quality of fast-food restaurant items and has led researchers to conclude that eating out plays a major role in childhood obesity.

"The number of meals and snacks eaten away from home is believed to contribute to excess calories consumed by children, and this number has increased dramatically in the past 30 years," said study co-author Kerri Boutelle. "On a typical day, a remarkable 30 percent of youth report consuming fast food."

The most frequently purchased menu items for preschoolers were fries, soda, chicken nuggets, cheeseburgers and hamburgers.

Children aged six to 11 were also eating hot apple pies and kids aged 12 to 18 added chocolate chip cookies to their lunches.

Researchers also bring particular attention to the fact that soda was purchased more often than milk.

And despite the availability of apple pieces or fruit parfaits, families overlooked these healthier options.

To carry out their study, researchers surveyed 544 families entering a fast-food chain restaurant inside Rady Children's Hospital in San Diego at lunchtime.

Families were asked to present their receipts and complete a brief survey and were given $2 for participating.

The report comes on the heels of a nationwide initiative in the US launched by the National Restaurant Association earlier this month, Kids LiveWell.

Participating restaurants include Burger King, Au Bon Pain and IHOP and have pledged to offer a children's meal with 600 calories or less. Other requirements call for a well balanced meal with two servings of fruit, vegetables, whole grains, lean protein or low-fat dairy, with limits on sodium, fats and sugar.

Meanwhile, another study from the July issue of the American Journal of Clinical Nutrition found that people tend to eat more nutritious meals at home than when dining out.

Researchers speculate that when people are in their comfort zone, they're more often than not in a good mood and therefore tend to prepare healthier meals.

For  a full list of participating Kids LiveWell restaurants, visit http://www.healthydiningfinder.com/kidslivewell/index.