Apartment hunters have long been aware of the convenience of homes close to public transportation, but a new study shows that New Yorkers who live near bus stops and subway stations also weigh less.

“At it’s simplest, if you walk to the corner store to buy your quart of milk, you are expending energy,” an author of the study, Andrew Rundle, said. “If you have to drive to the supermarket, you are not really expending any energy.”

He said that in terms of proximity to public transportation, “the idea is, if you have access to public transportation, you can be independent of your own personal car. You’re going to walk to the bus stop.”

In a comparison of 13,102 city residents, researchers from Columbia University’s Mailman School of Public Health found that those with the lowest body mass index levels lived close to buses and subways, in densely populated areas, and in neighborhoods with mixed residential and commercial uses.

In fact, they reported, there was an 0.86-unit difference in BMI levels — a measurement that takes into account a person’s height and weight — between individuals living in the most and the least densely populated areas, according to the study, which will appear in the March/April issue of the American Journal of Health Promotion. If all New Yorkers subtracted half a unit from their BMI level, it would average out that 10% of overweight people would be normal weight, researchers said.

The findings confirmed what nutritionists and other health experts have been saying for years, several said yesterday. “It endorses what I’ve been telling my patients, that it’s always best to walk and that walking can help them to maintain a healthier weight,” the president-elect of the New York State Dietetic Association, Keri Gans, said. She said a 140-pound woman is able to burn 100 calories by walking briskly for 15 minutes.

Still, skeptics initially questioned whether those who live closer to public transportation are less likely to walk very far to catch their buses and trains.

“Generally, transportation promotes being overweight,” a professor of nutrition at New York University, Sharron Dalton, said. “As a subway rider every day, there are a lot of big people on the subway. I notice that all the time, because I fit into the seats and a lot of people don’t.”

Still, she said, “Maybe in a crowded city, it’s a sign that to use public transportation you have to walk a little to use it.”

Others agreed. “It encourages that little bit of activity, even if you are going up and down the subway stairs a few times a day,” a registered dietician in Manhattan, Elisa Zied, said. “That adds up to calories burned,” Ms. Zied, author of “Feed Your Family Right!,” said.

Still, she cautioned, “New York is not typical of America, and you have other extremes, as well … I think people have a heightened awareness of themselves in New York and probably don’t succumb to the temptations the way other people might.”