Apart from being glamorous, rail-thin, celebrity clothes-horses, what do Sarah Jessica Parker, Anna Wintour, and Julianne Moore have in common?
Answer: they're all New Yorkers. And more specifically, they're all Manhattanites.
Anyone who's spent time in the Big Apple's most famous borough will have seen women just like this browsing the size zero rail in Bloomingdales or striding the sidewalk in their skinny jeans and bare arms, looking as if they might snap in two if the wind picked up.
Their svelteness is all the more remarkable in a city famous for its top-notch restaurants, all-night diners, coffee houses and sumptuous cocktail bars. Just how do they do it?
Now their diet secrets have been picked over by New York writer Eileen Daspin, whose new book The Manhattan Diet is a guide to the eating habits of its super-thin residents.
Daspin got the idea for the book when she read a New York Times report which confirmed what she'd long suspected: the residents of Manhattan are skinnier than those of all the other city boroughs.
Daspin -- she's a Manhattan resident, a lifelong dieter and married to a top chef, giving her ample opportunity to dwell on the city's twin obsessions with looking good and eating well -- interviewed more than 100 New York women to find out their skinny secrets.
And 25 of the women wrote daily food diaries, so that Daspin could analyse exactly what, and exactly how much, they ate each day.
The big secret? Portion control, coupled with the healthy amount of walking most New Yorkers do to get around their city.
Daspin found that, by and large, these women weren't denying themselves what they wanted to eat -- instead, they were eating wholesome food, but only in small amounts.
"The thing is to really like what you're eating and not to eat too much of it. The women I interviewed didn't waste calories on junk foods. But they were really being careful with what goes in their mouths."
Careful might just be understating it. Some of Daspin's interviewees were vigilant to the point of extremity.
One hadn't eaten a carbohydrate since 2007. Another recommended eating with chopsticks to slow down your food intake. And another poured water over leftovers to ensure she wouldn't give in to temptation.
"I don't think that I am advocating those extreme things," says Daspin. "But I do think that in some small way there is something to be learnt from this kind of hyper-awareness."
The book has attracted accusations that it glorifies eating disorders. In particular, critics seized on an admission Daspin made in the book: "I taste everything but eat almost nothing," she wrote.
But the remark, she explains, has been taken out of context. As the wife of a well known chef, when they go to restaurants together, they are often sent 15 or 20 dishes to try.
"I am a normal size, I'm not overweight, but I'm not super-skinny. So I taste everything, but if I finished all those dishes, I'd be humongous," she laughs.
"The main thing is to eat throughout the day. A lot of the women whose diets I tracked had mini meals throughout the day -- they had something at 7am, something at 9, something at 11. This constant grazing helps keep up blood sugars."
Daspin recommends filling up with healthy grains such as quinoa, spelt and rye and to really listen to your body. If you're hungry, eat. And if you feel like something sweet, have it.
In fact, Daspin says she was taken back by just how often the women she interviewed treated themselves.
"I was surprised by the amount of candy that people ate. In the afternoon, they might have a few gummi candies or one of the tiny Reese peanut butter cups. It's about not depriving yourself."
The other important element for Daspin's slim New Yorkers is exercise: many are gym devotees who push themselves to the limit at back-to-back spinning classes.
But the exercise involved in simply going to work each day, trotting up and down the stairs of the subway stations and walking miles around the city plays its part too.
"It's good for your heart," says Daspin. "And as well as that, when you're walking you're exposed to other people.
"We are out and about a lot checking each other out. When you're out and see these people who look fantastic, and you want to look like that. It's the competitive thing."
It helps, of course, that New York is home to industries which have long celebrated skinny women.
"Fashion is based here, the advertising and publishing industries are here -- we have lots of image-conscious industries. It's very wealthy here too. And a lot of trends start here. Exercise, food and diet are very important, and there's that whole Sex and the City thing of looking good."
As for the good things in life, nearly all of the 25 women who kept food diaries for the book had a glass of wine a few times a week.
So when it came to devising a diet plan for the book, Daspin was keen to include a little alcohol.
"The nutritionist I was working with questioned that, she said it wasn't the healthiest. But that's what people were doing, and I wanted to be realistic. The thing is, a glass of wine is fine, but if you're drinking a bottle, you've got a problem."
Daspin herself says she has learned a lot from the city's residents. "I've lived here since 1980, and since I've moved here, I have lost 25 pounds. Gradually, I changed the way that I do things, and the weight came off.
"When I was doing the research for this book, I really listened to what the women I talked to said, and then I tried to adopt their wisdom.
"For instance, I'm a working mum and it's often a stretch to get dinner on the table.
"But now I make sure to keep brown rice and beans ready, so that I can pull together a nutritious meal quickly."
The Manhattan Diet: Lose Weight While Living a Fabulous Life is out now, published by Wiley