|USA and Canada|
|Dawn Zier, President and CEO|
|Products||weight loss, weight management, nutrition|
|Services||telephone, Internet and mobile counseling for weight control|
Nutrisystem is a commercial provider of weight loss products and services headquartered in Fort Washington, Pennsylvania. Nutrisystem's initial product in 1972 was a liquid protein diet, but the company changed its offering after Slim-Fast came to prominence in that market. The company originally offered weight loss counseling and products in brick and mortar centers, but in 1999, Nutrisystem moved to a direct-to-consumer business model, selling its products and programs on the Internet and by telephone.
In 2012, Dawn Zier joined the firm as CEO.
In 2015, thefirm acquired the South Beach Diet brand. In December 2018, Tivity Health announced that it would acquire the Nutrisystem brand. On October 19, 2020, Kainos Capital acquired the brand from Tivity Health.
Efficacy and criticism
A systematic review in 2015 concluded that Nutrisystem "shows promise" because, in the short term, studies have shown that Nutrisystem was more effective at weight-loss than a control group, but found no studies of long-term efficacy. 
As of 2019[update], four weeks of a basic Nutrisystem plan costs the average American customer $274.99. In light of this expense, the Mayo Clinic lists one of the disadvantages of the diet to be its potentially "prohibitive" cost. Obesity specialist Fatima Cody Stanford writes that a potential disadvantage of the diet is that it complicates social eating because a person following the Nutrisystem plan has to follow a distinct dietary program.
- Longe JL, ed. (2008). "Nutrisystem". Gale Encyclopedia of Diets. Volume 2. Gale Group. pp. 722–726.
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- "United States Securities and Exchange Commission Annual Report Form 10-K".
- Brandy, Shaul (24 April 2015). "Nutrisystem Launches Weight Loss Platform on IOS". AdWeek SocialTimes. Retrieved 18 May 2015.
- Fair, Matt (1 July 2014). "Nutrisystem Accused of Stealing Rival's Diet Mobile App Technology". Law360. Archived from the original on 22 May 2015. Retrieved 18 May 2015.CS1 maint: bot: original URL status unknown (link)
- "Webdiet Inc v. Nutrisystem Inc". Retrieved 20 November 2020.
- Key, Peter (5 November 2012). "Dawn Zier named president/CEO of Nutrisystem". www.bizjournals.com. Retrieved 2019-11-27.
- Hilario, Kenneth (18 December 2015). "Nutrisystem acquires diet brand for $15M". www.bizjournals.com. Retrieved 2019-11-27.
- Hammond, Ed (10 December 2018). "Tivity Health Plunges With $1.3 Billion Nutrisystem Deal". Bloomberg. Retrieved 2019-11-27.
- "Tivity Health Announces Sale of Nutrition Business". October 19, 2020.
- Gudzune KA, Doshi RS, Mehta AK, Chaudhry ZW, Jacobs DK, Vakil RM, Lee CJ, Bleich SN, Clark JM (April 2015). "Efficacy of commercial weight-loss programs: an updated systematic review". Ann Intern Med. 162 (7): 501–12. doi:10.7326/M14-2238. PMC 4446719. PMID 25844997.
Nutrisystem demonstrates better short-term weight loss than control/education and behavioral counseling; however, we identified no long-term trial results. We conclude that Nutrisystem shows promise, but the lack of long-term RCTs prohibits definitive conclusions.
- Stanford FC. "Chapter 10: Weight-loss programs". In Stevens JR, Stern TA (eds.). Facing Overweight and Obesity: A Complete Guide for Children and Adults. MGH Psychiatry Academy. pp. 127–128. ISBN 978-0-9991483-5-8.
- "Weight loss: Choosing a diet that's right for you". Mayo Clinic. 6 June 2020.