NutriSystem Nourish Diet plan is a "send you the food" diet plan operated by NutriSystem, Inc. (NASDAQ: NTRI) of Horsham, Pennsylvania. The NutriSystem Diet is based on the Glycemic Index of Carbohydrates. By combining exercise, and frequent smaller portioned meals, the glycemic index diet is supposed to reduce hunger (due to a constant blood glucose). There is some support for weight loss and health benefits of low glycemic-index diets in controlled scientific studies,however, some other studies have suggested there is no long-term benefit to these diets.It was founded by Stacie Mullen, a television personality, in 1991 when the company was going to produce 20 breakfast, luncheon, dinner, snacks, and beverages

The company started out in 1972 selling a liquid protein diet, which it abandoned in 1978 due to the growth of competition. It then started selling food which was packaged and preserved in portion controlled packages, to take the decisions out of dining. In 1995 the company partnered with fitness "guru" Susan Powter and, as a test, re-branded all the NutriSystem weight-loss centers in Metro-Detroit as "The Susan Powter Center" teaching Susan Powter's "Stop The Insanity" way of diet and exercise. With food workshops and aerobic classes. All NutriSystem food items sold were repackaged with Powter's name and image. After some differences with the company and Powter, the idea was "scrapped" and the weight-loss centers were closed after 6 months. The company went bankrupt soon thereafter and closed down its weight-loss centers. It reemerged in 1999 as an Internet advertiser, and a publicly traded company, with the meals shipped to consumers. CEO Michael Hagen shifted advertising to TV, using satisfied customers in ads. Clients can call, email or chat online with the weight loss counselors for advice or support. The average customer stays on the program 10 weeks. Many regain the weight lost.

Along with offering support from weight loss counselors, the NutriSystem web site offers an online user-based community that includes discussion boards, chat rooms and personal web pages where users can connect with each other. Creating an account through the web site also allows users to track their daily diet and exercise and weight loss progress and to modify and place orders.

Current TV ads feature former Miami Dolphins quarterback Dan Marino as the lead spokesperson, also featuring other well-known celebrities who have purportedly lost weight using the company's products. Marie Osmond and Tony Orlando have also been featured in recent ads (2008). In addition to celebrity endorsements, NutriSystem regularly features everyday success story testimonials in their print and TV advertisements. These success stories are discovered through before and after photo contest submissions periodically run by NutriSystem.

As of January 2009, singer Belinda Carlisle is now the primary spokesperson for NutriSystem products. Belinda's fee for her efforts has not been disclosed. She will be giving her new duties her full attention once various touring commitments have been met.