Hi Ambika,
I agree with Bhavini. To lose 15 pounds in 7 days, is not possible naturally, if still you want to go for then surgeries are the only option left. Surgeries like gastric bypass, gastroplasty, Liposuction etc. can be done to lose weight, but all these surgeries comes with complication and there is no Guarantee that further weight gain will not be there. The best and safest way is an holistic approach of low caloric diet, regular exercises and active lifestyle.