Rad, something I specialize in. I'm one of those fancy tea connoisseurs that lingers over on Steepster, and did a lot of research on green tea due to the huge media coverage last year. I read tons of research papers that were clinical trials for Catechins, and in a nutshell, you would have to drink 40 cups of green tea a day to get the claimed results (it was around 40...I'm not good with remembering details). Now, this is a double-edged sword, because out of all of the teas (oolong, white, black, silver needle...etc) green tea is the WORST about causing oxidative stress in large quantities. If you aren't familiar with oxidative stress, it is the precursor to every single terrible thing your body can have....think Miracle Grow for cancers, Alzheimer's, Parkinson's, SCD...etc. As a perk about oxidative stress, it DOES prevent the physical aging process, but it seems to do it in a bad way. Don't let this seem like it's a bad thing though, because this is from extreme and/or long-term consumption. I wouldn't give it two thoughts when it comes to drinking green tea, but I wouldn't be first in line to dump a cup of matcha on my ice cream everynight. Obviously all teas promote weight loss via caffeine, but I was never able to trace the roots of the claim that green tea is better at weight loss... in fact it should, in a psychopharmacological way, be the second worst tea to help with that since almost every other tea has significantly higher caffeine content (excluding Rooibo of course since it isn't actually apart of the Camellia family).
Sorry, I may have nerded out a bit, but I find it to be a very fascinating topic in every aspect. Another fantastic tea that honestly has more beneficial properties is Silver Needle, which is honestly the snobby way to say "the very tip top buds of the white tea plant". It also has less caffeine in it than even green tea for those that are not drinking it for the caffeinated properties. My favorite is oolong which is sort of in between black and green if you want the green tea theory with extra caffeine.
Being a high-end tea collector, I have hundreds upon hundreds of tea samples of any orgin you can imagine.... if anyone wants to try anything in particular, just let me know, and I'll send you anything you want to try for free (enough to make a few cups). I'm always happy to help expand the tea community . EDIT: It's important to mention that I'm not selling any of my teas.