Thank you for your question. I find that many patients in consultation will cite that they have some weight that they wish to lose in the hopes of reaching a target number. For fluctuations anywhere from 10-20 lbs, this is generally not an issue if it occurs post-op but every patient is different and should be evaluated on an individual basis. Generally speaking, for patients who have lost a significant amount of weight in the past, it is recommended that they wait until their weight has stabilized before undergoing a cosmetic surgical procedure, breast augmentation included. Historical trends in how and from what areas a patient generally looses weight, skin tone and elasticity, and how realistic achieving a proposed weight-loss is for a given patient should all be considered. To answer your question, weight loss will not have any effect on your breast implants. Weight loss can however affect the appearance of your breasts, as weight loss can lead to changes in breast tissue which can cause breast ptosis or breast droop. I would recommend scheduling a consultation with a board-certified plastic surgeon to discuss the options available to you and to get the best recommendation as to when you should proceed with the proposed procedure in your specific case and given your desire to loose roughly 20 lbs. I hope you find this helpful and I wish you the best of luck!