So-called body-contouring procedures are increasing in popularity, rising 43 percent from 2017 and quadrupling since 2012, according to a 2019 report from the American Society for Dermatologic Surgery. (And those figures include only a fraction of the hundreds of thousands of fat-erasing treatments done at medical spas.)

For every one liposuction, there are more than 10 noninvasive body-sculpting treatments, according to the A.S.D.S. The genre includes fat-melting treatments via laser (brand names like SculpSure), radio-frequency (truSculpt, Vanquish) and ultrasound (Liposonix).