What the Experts Say continued...

Motivated dieters can benefit from the lifestyle tools, educational materials, and online support. But Farrell fears that some people will just eat the food and hope that by some miracle, they will improve their eating habits after finishing the program.

"The NutriSystem plan is great for a short-term approach, but eventually you have to do the work by yourself, so pay attention to the portion sizes and food preparation styles so you can learn from them and do it on your own," says Farrell.

She suggests slowly transitioning to planning and preparing your own meals.

"One of the most important aspects of weight control is learning how to shop and cook healthier foods, and this program does not accomplish that critical aspect," she says.

Farrell likes the way the plan promotes eating regular meals and snacks, but is concerned that there may not be enough calories.

"There may be too few calories to manage hunger," she says. "Some meals are 250-350 calories whereas others are only around 150 calories -- and that is fine for a snack, but not enough for a meal."

Experts' opinions are mixed on the glycemic approach to weight loss. Some think it's just another gimmick -- but say that if it helps people eat in a more healthy way, the gimmick can be successful.

For example, nationally known diabetes expert and author Marion Franz, MS, RD, CDE, says that while the glycemic index is useful for people with diabetes, it has no redeeming value as a weight loss tool.  But Harvard endocrinologist and pediatric professor David Ludwig, MD, says he has successfully used a glycemic index-based diet plan to help many children and families lose weight.

Food for Thought

Singles, people on the go, or anyone who does not want to be bothered with cooking may find this low-calorie, nutritionally sound program an easy, short-term way to lose weight. And following the plan and controlling calories with healthy snacks and supplemental items should result in weight loss. The 12-week mindset and weekly newsletters can be helpful in changing behavior, but won't help you prepare your own meals when you re-enter the real world at the end the program.

Think of the NutriSystem diet as a temporary plan that can help get you started on the road to healthier eating, but keep in mind that you will ultimately have to do it on your own. The challenge is to continue losing weight on a calorie-controlled diet without the advantage of the prepackaged foods.

Kathleen Zelman, MPH, RD, is director of nutrition for WebMD. Her opinions and conclusions are her own.