Nancy Brueheim wishes she could break 100 pounds. Without working at it, Brueheim, who is 71 and stands 5-foot-2, fluctuates between 95 and 98 pounds.

The Martinez, Calif., mother of four always has been thin, even as a child. In fact, she comes from a long line of petite women who lived into their late 90s. Brueheim indulges in the occasional hamburger and, save for a food allergy, is free of disease and prescription drugs.

But the skinny life has its challenges. Clothes are difficult to find. And Brueheim has heard a lifetime of hurtful comments. "I'm healthy, I have a lot of energy, and yet people will say such things, like, 'Gosh, you need to eat more.' We'd never say such things to an overweight person," she says.

You know the stereotypes. If someone is very thin or underweight, we assume they are ill or have an eating disorder. Or a hollow leg, right? Maybe they live at the gym. All not true.

While genetics and ethnicity play major roles, there is no one-size-fits-all reason why some people are slim and remain so without really trying, says Kaiser Permanente registered dietitian Nora Norback.

Growing up in Ohio, Elizabeth Leary was so thin that kids would crank-call her home and tell her to take Nutrament, a nutritional supplement. The comments continued into adulthood. "People would say, 'You've got a string hanging off your dress. Oh wait, that's your leg,'" recalls Leary, now 61 and living in Pleasant Hill, Calif. Pregnancy, and the accompanying pounds, brought relief. "It just felt so good not to be teased all the time," she says.

Orinda, Calif., marriage and family therapist Margie Ryerson says even innocent comments about weight can be damaging.

"Even if it comes from a sense of caring, it's not appropriate and can create distress and unhappiness for the person," Ryerson says. "They can feel blamed and criticized. In our society, we associate control, will power and strength with thinness. But for people who are naturally thin, it causes them to feel bad about themselves. They're not trying to be the object of envy. And they don't want to have to explain themselves. Why should they?"

METABOLISM

Many thin folks, including Leary, point to a fast metabolism. Metabolism is influenced by many things, including gender (men have a slightly higher metabolic rate), hormones, sleep, exercise and use of stimulants such as caffeine and nicotine, Norback says. Also, some people simply have mild appetites, and must remind themselves to eat. Bottom line: Don't judge a body by weight, because it's not about numbers.

"It's about health," Norback says. "Healthy people do come in different shapes and sizes, but at the extreme ends, we certainly see more health problems. We make a lot of our judgments on how a person looks. But you shouldn't assume that someone is unhealthy if they're really thin."

To rule out eating disorders, Norback looks at a variety of factors beyond the scale, including body image, diet and malnutrition, hydration status and exercise frequency.

Certainly, it's important to remember that there are naturally thin people who make an effort and those who just are thin without trying a whole lot. Still, most share key lifestyle traits. Of the dozen interviewed for this story, including Brueheim, the majority love fruits and vegetables. Most avoid fast food and sweets. And, with the exception of two, they exercise frequently. If they enjoy these things, it's not work, they say. Some, like Kristin Ewart, 22, of Discovery Bay, Calif., don't do anything. Ewart is 5-foot, 2-inches, weighs 125 pounds and eats as much pizza and sweets as she wants, she says.

"I have my dad's genes," says Ewart, who wears a size 2 or 4. "I eat whatever I want, I sit on the couch, and I don't gain any weight."

Strangers have felt the need to tell Ewart what they think -- that she's too thin -- but she feels blessed. She hits the gym to tone up. That's all.

STOMACHS ARE SMALL, TOO

Brueheim does Pilates and walks up to three times a week. Any more cardio and she tends to drop weight. When that happens, she'll add bread to her diet. Fish, pasta and yogurt are her staples.

"What people also don't realize is that little people have small stomachs," Brueheim says. "A doctor once told me that a lean horse runs a long race. I like to remember that."

When Katrina Ritchie hit puberty, she lost 20 pounds and shot up like a bean pole. Her mother was concerned, but, besides a period of anemia in her 20s, Ritchie was and remains healthy.

Today, at 49, the Berkeley massage therapist is 5-foot, 11-inches and weighs 137 pounds. Ritchie's work is quite physical, but she still walks, stretches, and "dances around the house" to get her heart pumping. Clothes are not as easy. Her shoulders are so narrow that she has to buy her T-shirts in the boy's department at Target. What do her girlfriends say to that?

"They hate me," Ritchie says. "People say, 'You've got to be kidding me.' I can still fit into things I wore when I was 13."

Gwen Netha of Fremont, Calif., can still fit into a dress she wore nearly four decades ago. Netha, who is 61 and wears a size 0, is just under 5-foot-2 and weighs 103 pounds. She lived in Europe most of her life before moving to California nine years ago. But she still can't get used to the size of plates in restaurants.

"They're so big, it kind of turns me off," she says, adding that she prefers expensive restaurants, where quality trumps quantity. When people ask her "how she does it," she gives them the skinny.

"I don't diet but I've been exercising most of my life," she says. "I don't eat fast food. I've never had a hot dog. I don't drink soda. I enjoy eating salads and other things people turn up their noses at."

MOST ARE THIN THERE

Brandon Gan also loves his veggies. And whole grains. Despite his slender frame -- Gan is 5-foot-6 and weighs 120 pounds -- he has high cholesterol, so eating right is a must. When Gan was growing up in Malaysia, his father used to call him "chicken legs" when he'd wear shorts. But otherwise, no one made a big deal about his weight, because most people are thin in Malaysia, he says.

"I never really understood how skinny I was until I came here," says Gan, 26, who moved to the United States in 2002. "People here are more vain, and everyone wants to improve their bodies. When I came here, I'd hear it (skinny commentary), and I got a little influenced by the culture."

A few years ago, Gan, who says he was so thin his chest was concave, ate more to gain weight. He put on about 10 pounds, but didn't like the way his face looked as a result, he says.

These days, he swims, lifts weights and takes a protein supplement to build muscle. While he still weighs 120 pounds, he feels strong and toned. And, even though he wears boy's jeans and admits that he's "a little too skinny," he is not without his fat days. Seriously.

"I think I'm fat when I haven't done any physical exercise in a few days, or if I ate and drank too much the night before," Gan explains. "Whenever I complain that I'm fat, my roommate says that if I was any thinner, I'd be two-dimensional."

THIN, NATURALLY

Too many factors are involved in determining why certain people are naturally thin regardless of what they eat or if they exercise. But, here are some basics from experts, including dietitian Nora Norback of Kaiser Permanente Richmond, Calif.

Genetics. If mom or dad are thin, there's a higher chance you will be.

Metabolism. Influenced by factors including gender, age, stress and stimulant use.

Thermic effect of food. An estimate of the energy required to process food. It is usually 10 percent of energy (calorie) intake, but can be higher in some people.

Variations in appetite regulation. Some people have small or mild appetites and have to remind themselves to eat.

Ethnicity. Thinness is more common in some populations, such as Asians.

Eating right. Diets rich in fruits, vegetables, whole grains, lean proteins and low-fat dairy.

Exercising regularly. At least three times a week.

Explore further Study reveals food choices influenced by body types of dining partners

(c) 2009, Contra Costa Times (Walnut Creek, Calif.)

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