The programs are popular and successful, according to some studies. Rankings from Consumer Reports in 2011 placed Jenny Craig and Slim-Fast in the top spots of its list of best diets. A 2010 study published in the Journal of the American Medical Association found that 92 percent of Jenny Craig participants stuck with the program for two years, and weighed an average of 8 percent less than before they started the program.
"Jenny's clinically proven program that offers balanced menu plans as a model for proper portions," said chief executive officer Dana Fiser in a statement from the company.
But some nutrition experts say they find a dieter's reliance on prepackaged foods unpalatable.
"Most of these diets do not address the lifestyle changes needed to improve health bur rather attempt to simply rein in bad habits with smaller portion sizes or with pre-packaged food products," said Susan Levin, director of nutrition education for the Physicians Committee for Responsible Medicine.
Beth Kitchin, a dietician at the University of Alabama at Birmingham, said she recommends that dieters stick to real foods and smart portion sizes, but said some products can offer an easy way to get people to begin much-needed weight loss.
"Would I love to eat home-cooked healthy meals every day, every meal? Sure, but who's got the time?" Kitchin said. "We need to be practical and pragmatic when it comes to eating healthfully."
A DASH Under Easy
The DASH diet took home U.S. News and World Report's prize as the best overall diet, but barely missed a spot on the list of easiest diets, earning 3.1 out of 5 points in that category.
"DASH is actually awesome. It's pretty realistic, it's not bizarre. It just asks people to eat a lot of fruits or vegetables and low-fat or non-fat dairy, which really is how I measure the quality of a diet," Ayoob said. "It's not inhuman."
DASH -- Dietary Approaches to Stop Hypertension -- was originally designed to help people lower their blood pressure by controlling their sodium intake, cholesterol and triglycerides. Several studies have shown that the diet is successful in improving heart health.
Katz said DASH is a moderately easy diet, but it doesn't have the support that some of the other diets have, which may be why it ranked lower on the list.
Overall, experts say the list of easy diets can be an important tool to give dieters options for how they can begin to lose weight and stay healthy.
"There's more than one healthy diet," Ayoob said. "But people have to accept that you have to take a hands-on approach."