A US advocacy group has demanded the Federal Trade Commission take action against Coca-Cola and Nestlé for unlawful deceptive advertising for Enviga.

The Center for Science in the Public Interest (CSPI) says the companies' claim that the green-tea-flavoured diet soda burns more calories than it delivers implies weight loss, which the companies refute, marketing it rather as a way to promote better health and a drink that "allows you to burn calories."

CSPI is also suing Coke and Nestlé in federal court on the issue, saying there's no basis for weight-loss claims, adding the commission has ruled such claims not mentioning the need for increased physical activity or decreasing caloric consumption are inherently deceptive.