Consuming only green tea will not help you much...you should add other dietary restrictions and exercise to that....Green tea or green tea extracts containing 150 to 2500 mg catechins, taken in single or 2 divided doses daily for up to 24 weeks, has been used to reduce weight....Weight gain happens either due to addition of extra calories or due to failure to spend calories consumed...these extra calories deposited in our body as fat..for weight reduction you have to consume less calories and spend more...avoid junk foods,carbohydrates like rice etc,avoid oily foods...add proteins and fibre rich foods to your diet with green leafy vegetables, fruits...do regular exercise at least 2 hours a day...Consult dietitian they will do the needful.