TL;DR: Green tea can be effective for fat/weight loss.

It is well known that green tea is rich in antioxidants and other minerals that are beneficial for health. If you are overweight (for your height, etc.), it is possible this is a result of excess sugar in your diet. By consuming green tea regularly, you will likely be replacing this sugar intake with tea which contains no sugar (unless you add some) and is beneficial to your health. Thus, over the long-term, it should be effective in making your lifestyle healthier (and causing fat loss) provided that you don’t fill other parts of your diet with junk foods and other harmful substances.

Tea in general is good for you and can be used to substitute sugary drinks/soda and curb your diet. Regular consumption of green tea is said to help with lethargy (makes you feel more energetic), etc. and can really change the way you approach your day.

You can also check out this study by Harvard on the health benefits of green tea: Flavonoids: The secret to health benefits of drinking black and green tea? - Harvard Health

Note: This is an opinion based on logic and experience and not scientific fact. If you do not maintain a healthy lifestyle outside of consuming green tea, it will not result in any fat loss or external health benefit.