He may not be in the triple-digit league of Deborah Voigt, but the music director of the Metropolitan Opera and Boston Symphony Orchestra, James Levine, now has his own pound-shedding success story to tell.

After recovering from a rotator cuff injury sustained in a fall in March, Mr. Levine will return to the podium for the opening of the Tanglewood season next week 35 pounds lighter. And he says he plans to lose 15 more pounds over the summer.

There were no diet pills or surgery for Mr. Levine. He lost the weight through the old-fashioned combination of a nutritious diet and increased exercise. He rode a recumbent bicycle, walked, and, under the supervision of a trainer, took up stretching and Pilates.

Fewer late nights and dinners out helped, too. “Restaurant eating and portion sizes are so out of control,” a senior clinical dietician at Mount Sinai Hospital, Rebecca Blake, said. “People tend to say,’Well, the food’s on my plate and I’m paying for it, so I have to eat it all.’ That’s really what has led to a lot of the obesity problem.”

Mr. Levine said after his injury in March that he planned to use his forced vacation to focus on his health and on losing weight.

In the opera world, of course, Mr. Levine is in good company with his weight problems. Other conductors, too, have battled the bulge.

The chief conductor of the Sydney Symphony, Italian maestro Gianluigi Gelmetti, has spoken about his efforts to lose weight. And the music director of the Columbus Symphony Orchestra, George Del Gobbo, used his dieting as a novel form of fund-raising, asking donors to pledge a certain amount of money to the symphony for every pound he lost.

Some conductors have an easier time staying fit. The music director of the New York Philharmonic, Lorin Maazel – who, at 76, is 13 years Mr. Levine’s senior – stays trim by playing tennis.

Whether because of the late nights, the stress of touring, or the loneliness of pursuing a singing career, many opera singers struggle with their weight. Luciano Pavarotti in recent months has canceled a string of tour dates because of lower-back issues aggravated by his heft.

The question of the best weight for singers is a fraught one, as it sits at a nexus of health, vocal strength, and marketing.

The soprano Deborah Voigt decided to have gastric bypass surgery in 2004, after she lost the leading role in Strauss’s “Ariadne auf Naxos” at the Royal Opera House in London because she couldn’t fit into the little black dress the director envisioned. After surgery, she lost about 135 pounds. She said she was pleased, but critics speculated that the weight loss would affect her voice.

After the tenor Ben Heppner lost 100 pounds in 2002 and 2003 for the sake of his health, some critics found him gaunt and his voice attenuated. Mr. Heppner has since regained much of the weight he lost.

The editor of Opera News, F. Paul Driscoll, warned against drawing too simple a connection between a singer’s weight and vocal strength. “If someone really knows how to sing and has a solid vocal technique, that will stand him or her in good stead no matter what the weight is,” he said. “If someone has a flawed technique and flawed support, then weight loss, especially very rapid weight loss, can highlight that.”

He cited the case of Maria Callas, whose voice, critics said, suffered after she lost weight. Mr. Driscoll said he thought the connection was overstated. “Joan Sutherland and her husband, the conductor Richard Bonynge, both maintained that there were some performances when Callas was heavy when she sang unsteadily, and there were some performances after she’d lost a great deal of weight where she was solid as a rock,” he said.

But Mr. Driscoll said the demand that singers look like television stars, to make opera appealing to popular audiences, was harmful to the art form. “There are certain requirements for impersonating a character on television or on film which should not be the no. 1 priority when it comes to hurling sound in auditoriums that hold 4,000 people,” he said. “Marketing professionals prefer people who look like the parts to represent opera. I don’t know that that’s a good long-term solution for the health of opera,much less the health of the individual singer.”

For Mr. Levine, as a conductor rather than a singer, being slimmer at the podium has no downsides. But health professionals warned against overemphasizing weight loss as a cause of good health, rather than a result of it.

“Weight loss usually is one of the last things that happens when you get healthy,” a holistic health counselor, Amara Wagner, said. “You change your mind-set, change your lifestyle, change what you eat, and then you lose weight.”

So when Mr. Levine returns to the Metropolitan Opera in the fall, perhaps he should make an announcement about how his workouts are going and how many Pilates teasers he can do.