Grapefruit and green tea are rich in beneficial plant chemicals called polyphenols, making them healthy foods to include in your diet. The author of an article published in "Chemico-Biological Interactions" in January 2011 suggested that both of these foods may be beneficial for weight loss because of their high polyphenol content. Research results are conflicting, however, on whether this is actually the case.
A study published in "Metabolism" in July 2012 found that eating half of a grapefruit before each meal for six weeks didn't cause a significant amount of weight loss, with study participants losing only about 1.3 pounds. Green tea consumption also seems to lead to only small amounts of weight loss, ranging from 0.4 pound to about 7.7 pounds over the course of about three months, according to a meta-analysis published in "The Cochrane Library" in 2012. With results like these, you can't rely on drinking green tea or eating grapefruit to bring about any large changes in your weight. If you take any medications, speak with your doctor before adding grapefruit to your diet because it can interact with a number of medications and potentially cause adverse effects.