A Cochrane meta-anylsis including 14 studied involving use of green tea found that its consumption was associated with mild but significant weight loss results compared to controls or placebo. (2) One study that tested the effects of green tea extract on a group of adults compared to a control group not taking green tea found that after 12 weeks, those taking 857 milligrams of green tea had significantly lower levels of ghrelin (known as the hunger hormone).
Mansour, M. S., Ni, Y.-M., Roberts, A. L., Kelleman, M., RoyChoudhury, A., & St-Onge, M.-P. (2013, October 1). Ginger consumption enhances the thermic effect of food and promotes feelings of satiety without affecting metabolic and hormonal parameters in overweight men: A pilot study. Metabolism, 61(10), 1347–1352. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3408800/