Body-contouring procedures — nonsurgical treatments that promise to freeze fat or build muscle while you lie there — are soaring in popularity. Are they for real?

To Laura Salter, a fashion and lifestyle blogger, it seemed that no amount of diet and exercise would shrink her love handles or inner thighs. She thought that what she called the “obvious bulges” in her clothing were affecting her self-confidence and thus her work, but liposuction wasn’t an option. She has three children and no time for recovery.

So in February 2018, Ms. Salter, 42, decided to have her fat frozen off, paying $2,400 — yes, a blogger who paid — for a roughly two-hour cryolipolysis, or fat freezing, session. (Fat cells freeze faster than skin cells, so a roll of it can be clamped by a machine and literally frozen to death.)

Agony level: five minutes of “Ooh, this is awful,” she said, until each part went numb, followed by 20 minutes of “sharp, stabbing” post-treatment pain as the nerves thawed.

She was back in spin class two days later, feeling a little bruised. CoolSculpting, the brand name for the treatment, had promised results in two to three months, and sure enough, at the two-month mark Ms. Salter suddenly noticed the fat was gone — by her own measurement, one and a half inches off each thigh and half an inch off each love handle.