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.

WebDiet, Inc., a Silicon Valley startup, accused Nutrisystem of stealing their technology, but the case was dismissed in May, 2014.

[12] As of 2019[update], four weeks of a basic Nutrisystem plan costs the average American customer $274.99.

[13] In light of this expense, the Mayo Clinic lists one of the disadvantages of the diet to be its potentially "prohibitive" cost.