Linda Poskanzer was having a tough time in her late 60s.

“I was not doing well emotionally,” she recalled. “Physically, I didn’t have any stamina. I was sleeping a lot. I wasn’t getting to work.”

A therapist in Hackensack, N.J., Ms. Poskanzer was severely overweight and grew short of breath after walking even short distances. Her house had become disorganized, buried in unsorted paperwork. The antidepressant she was taking didn’t seem to help.

Her son, visiting from Florida, called his sisters and said, “Mommy needs an intervention.”

One of her daughters made an appointment with a geriatrician — a physician who specializes in the care of older adults. Dr. Manisha Parulekar, now chief of geriatrics at Hackensack University Medical Center, suggested her new patient take action on several fronts. She arranged for a sleep study, which found that Ms. Poskanzer suffered from apnea. She prescribed a different antidepressant, and physical therapy in a pool to help rebuild her stamina.

And weight loss. Eventually, the geriatrician agreed that bariatric surgery made sense. Over nine months, Ms. Poskanzer lost 75 pounds; she has shed another 15 since.