The Upper East Side is one of the city’s wealthiest and healthiest neighborhoods. It has one of the highest life expectancies, and among the lowest rates of diabetes and obesity in New York City. Now the neighborhood’s residents are getting even thinner.

Last year, about 2.3 percent of people living along a stretch of Manhattan that extended from the Upper East Side down to Gramercy Park were taking Ozempic, Wegovy or Mounjaro — injectable medications belonging to a breakthrough new class of weight loss and diabetes drugs, according to an analysis by Trilliant Health, a health care analytics firm.

That was the highest rate in New York City.

In some parts of Brooklyn, by contrast, where diabetes and obesity are far more prevalent, the usage rate of these medications was just over half of what it was in affluent parts of Manhattan, according to that analysis.

“The running game show of the 10021 ZIP code is guessing who is on Vitamin O” — that is, Ozempic, said the writer, actress and Upper East Side native, Jill Kargman, referring to what has long been the city’s toniest ZIP code, covering much of the East 70s.

The analysis by Trilliant Health offers the most granular glimpse to date of who in New York City is using these medications. It also highlights a divide along socioeconomic lines in who has access to the drugs, which are in high demand but in short supply.

In the Brooklyn neighborhood of East New York, for example, which has some of the city’s highest diabetes rates, about 1.2 percent of people were on these injectable medications last year.

“We have medications that have the ability to have clinically significant results, but we are facing barriers in terms of access and availability,” said Dr. Priya Jaisinghani, an endocrinologist and obesity specialist at NYU Langone Health. “My hope is in the future, this is more accessible to those who really need it.”

In most neighborhoods in New York City, between 1 and 2 percent of residents were taking these medications last year, the analysis found. But in a few areas, the rates were above 2 percent. Those included places with elevated rates of obesity or diabetes, like southern Staten Island and the Northeast Bronx. But they also included some of the wealthiest and healthiest parts of the city, including the Upper West Side as well as the Upper East Side.

The medications regulate blood sugar and insulin, suppress appetite and cause the stomach to empty slowly, increasing the sensation of fullness. They hold great promise for reducing obesity and diabetes, which disproportionately affect Black and Hispanic New Yorkers (and, in the case of diabetes, Asian New Yorkers) more than white New Yorkers.

These medications are expected to reduce health disparities that cleave along race and class. But for now, access to these medications is itself becoming a disparity.

In New York, Medicaid — the government insurance program primarily for lower-income residents — generally will not pay for these medications for weight-loss purposes, meaning often only those with diabetes are covered.

Employer-sponsored insurance plans, often referred to as “commercial insurance,” sometimes cover these medications for weight loss as well as diabetes.

“Patients with commercial insurance have greater access to these medications,” the obesity medicine director at Mount Sinai Hospital, Dr. Reshmi Srinath, said.

New treatments often first benefit people who have higher incomes, top-notch health insurance or easy access to good doctors. That was the pattern that played out in recent years during the first months of the Covid-19 vaccine rollout and with prescriptions for PrEP, which is taken to prevent H.I.V. infection.

The analysis by Trilliant Health shows that in predominantly minority neighborhoods, these medications are mainly making their way to people with diabetes. In the South Bronx, which encompasses some of the city’s poorest neighborhoods, about 73 percent of people on these medications had diabetes, which suggests fewer patients are receiving these medications for weight loss alone.

But in some of the city’s wealthier enclaves, under a third had diabetes, Dr. Allison Oakes, Trilliant’s director of research, noted. In those neighborhoods, these medications were prescribed primarily for weight loss. In parts of Manhattan’s east side, fewer than 27 percent of prescriptions went to people with a history of Type 2 diabetes.

The analysis from Trilliant Health is based on the company’s database of pharmacy and medical claims.

The company’s core business involves selling research and analytics to major hospital systems and pharmaceutical companies. It performed the neighborhood analysis at the request of The New York Times.

The analysis has some limitations. It divided the city into 34 zones that are often used by the Health Department for conducting surveys. That means that several neighborhoods are grouped together. For example, TriBeCa, one of the city’s wealthiest neighborhoods, is grouped with Chinatown and the Lower East Side, where poverty rates are higher than the rest of Manhattan.

While the company did not have access to the ZIP codes where patients resided, it did have the locations of pharmacies where each patient typically picked up prescriptions, allowing for estimates of where that person lived, said Dr. Sanjula Jain, Trilliant’s chief research officer. But this meant excluding some patients where residency was in doubt.

Additionally, the company only had access to prescriptions that went through insurance. Dr. Oakes noted that the study did not capture people who were willing to pay the monthly cost of $1,300 for some of these medications, or people using imitation drugs.

“If anything, this is an undercount,” Dr. Oakes said.

Since 2022, the year that the analysis covered, demand for the medications has skyrocketed.

“Patients are coming in, saying ‘I only need to lose 10 or 20 pounds,’” said Dr. Srinath.

The Trilliant analysis suggests that about 66 percent of people on these medications in 2022 were women. But the gender mix might be changing.

Dr. Srinath said that her patients had been predominantly women until recently. “I’m getting a lot more males over the last six months,” many in their 30s and 40s, she said.

In a few neighborhoods, including Borough Park and a swath of Manhattan’s west side that includes Chelsea and Hell’s Kitchen, men were nearly half of the patients last year.

The medications are already subtly changing the city’s circadian rhythms.

Jewell Paine, 25, who lives in Murray Hill in Manhattan and describes taking Ozempic on TikTok, says her social life used to revolve around food, but now she meets friends for movies or walks in Central Park. “It’s finding different things to do with my friends besides just going out to dinner or going out to drink,” said Ms. Paine.

Ms. Kargman, the writer, said she has noticed some friends at restaurants ordering a few plates for the table, “family style.” She suspects it is a trick to hide a new lack of appetite.

“They take a little bit and push the food around and they’re obscuring how little they’ve eaten,” Ms. Kargman said.

Olivia Bensimon and Asmaa Elkeurti contributed reporting.