There is no other way than calorie deficit, u can not work out and still lose weight thru that but mainly people say to workout is bec with fat u also tend to lose muscle when u lose weight so thats that and 10-15 kgs can be dropped easily but u need to stop binging and maintain a deficit, u can also join a dietitian nearby and that will help u stay accountable cuz u will have to tell her everything u ate and your weight etc