Your diet's at the door

There's no cooking; no calorie counting. Though costs of delivery diets run high, consumers are shelling out for them.

"Just last year it's gone up 33 percent, and they say it's going to be $1 billion this year," Tanya Steel, editor in chief of Epicurious.com, said about the sales of delivery diet plans.

Fresh ingredients can drive up the cost of plans to as much as $50 a day. The services may not be the most economically viable, especially for those with families who have to buy food for the rest of the household. But Steel said for people on the go, the cost may not add up to much more than a daily diet of take-out and Starbucks.

"If you take into account that you're buying breakfast on the go and coffee and then you're probably buying lunch at work, and then you're probably buying something at a fast food store or going to the supermarket, it probably evens out," she said.

Tips for Delivery Dieters

What makes the diet plans worth the cost? For most consumers, it's all about convenience.

"A lot of people these days don't know how to cook, frankly. And they don't know how to cook the right stuff. So this takes all the thought and preparation out," said Dr. David Katz, a nutritionist and Yale University professor. "Portion control is the second best thing about the pre-packaged meals. They provide a little bit of built in discipline here."

Some of the most popular plans include The Zone, eDiet, Pure Foods, Jenny Craig and Nutrisystem. Katz said while there's no perfect plan for everyone, consumers should look for the following when picking one:

Ingredients: Make sure the list is fairly short. With any packaged food, the longer the list of ingredients gets, the less good it is for you.

Chemical names: You don't want to be putting a lot of chemicals in your body, so stay away from anything with lots of long, unfamiliar chemical terms on the ingredients list.

Sodium content: The number of milligrams of sodium in a meal should be no higher than the number of calories in that meal.

Fructose: A lot of fructose or sugar in any meal is unhealthy.

Fiber: Fiber will fill you up without a lot of calories, so pick a plan whose meals are packed with it.

Delivery diets can help people establish healthy eating patterns, but Katz said they're not a long-term solution.

"As soon as you stop getting the home delivery meals, you're as senseless and clueless as when you started -- instead of learning how to read labels and portion control, you answered the door every morning and ate what they told you to eat," he said. "So if you're going to do this, fine -- but you need to also learn the good, healthy eating that's going to sustain you in the long run."

To see how Epicurious.com ranked five of the big national diet delivery services, visit http://www.epicurious.com/.