A study in Taiwan confirmed that people who drink an average of 1 (JUST ONE) cup of green tea a week were much healthier than people who drink energy drinks (or anyone for that matter) and weighed an average of 20lbs lighter than people who didnt drink tea.
I would be wary of studies like that and drawing loose conclusions. There is a bunch of unknowns that the researchers don't control for. You can't point to one thing and say that's the reason they weigh less. Maybe people who drink green tea regularly tend to have other behaviors that cause them to be healthy, like getting regular exercise and eating healthy foods. I doubt the researches controlled every aspect of their test subjects lives forcing the test groups and control groups to eat the same things and participate in the same activities. There is lots of really shady "research" conducted by, for example, green tea manufacturers.
I can almost guarantee this is how the "study" went.
Ring... Ring... Ring...
Test subject: Hello
Researcher: Hello wold you like to participate in a study?
Test subject: Sure!
Researcher: How much, if any, green tea do you drink?
Test Subject: 1 Cup per day! (or no cups)
Researcher: That's great! How much do you weigh?
Test subject: Why X pounds of course! (add ten pounds to stated weight if it's a female test subject

)
Researcher: Have a nice day!
Then USA Today picks up on the "study" and publishes it in their factoids section as "science".