A method and device for cosmetic surgery, especially fat reduction and collagen reformation, by means of a high power laser operating at about 980 nm is presented. The cosmetic surgery method substantially reduces or removes localized lipodystrophies, and essentially reduces flaccidity by localized laser heating of adipose tissue using an optical fiber inserted into a treatment area. The method and device are particularly well suited for treating Lipodystrophies with flaccidity High power laser energy is applied to "fat" cells to breakdown the cell walls releasing the cell fluid. The laser radiation is applied through an optical fiber which may be held within a catheter-like device having a single lumen. The optical fiber may have a diffuser mounted on the tip to further apply heating to tissues surrounding the whole tip. A saline solution may also be inserted into the treatment site to aid in the heating of the fat cells and their eventual destruction as well as their removal. The pool of cell fluid in the area of treatment is removed by a combination of techniques including allowing the body to remove it by absorption and drainage from the entry sites thus minimizing trauma to the area of treatment and hastening recovery. Additional techniques to remove the cell fluid include direct force application by means of elastic bandages and external suction applied to the entry sites. Quick and lasting cosmetic changes, even in areas having prior untreatable fat tissues, are achieved while minimizing trauma to the treatment areas.