All Credits go to Lorie Parch

How they get there, how they stay there.

Thin people favor bulky foods.

Barbara Rolls, a professor of nutrition at Pennsylvania State University, has done extensive research on “calorie density,” or the ratio of calories to the weight of food.

Simply put, foods with a high water content―fruits, vegetables, water-based soups and stews, and cooked whole grains―are low in calories but satiating. Most also contain lots of fiber (an apple has three grams; one cup of cooked barley has six), which fills you up.

Whether consciously or not, many thin people follow the strategy of starting out with a sizable soup or salad, which leads them to eat less for the rest of the meal. One Rolls-led study found that subjects who began a meal with a low-calorie salad―about 100 calories for three cups―were more likely to eat fewer total calories. “It subtracted about 12 percent of the calories from the meal,” she says. Foods with a lot of water, she adds, “can help you perceive that you’ve eaten more.” Drinking water with a meal, Rolls has found, doesn’t have the same effect. 

Thin people watch portion sizes.

No, most thin individuals don’t travel with a food scale and measuring cups or demand fat-gram counts from waiters.

But to keep an eye on what they eat without being obsessive, many focus on filling their plates with mostly fruits, vegetables, and lean protein. “No one ever got fat from a grilled shrimp,” says Stephen Gullo, Ph.D., a psychologist and the author of The Thin Commandments Diet (Rodale, $25, amazon.com).

They also use strategies such as buying just a single serving’s worth of food, eating portion-controlled frozen meals, passing up gargantuan-portion family-style restaurants, and using smaller-than-normal plates.

The National Weight Control Registry (NWCR), an ongoing study of how more than 5,000 people keep off the weight they’ve lost long-term, has found that successful weight maintainers tend to eat five small meals a day rather than three squares, which may make it easier to scale down portions.  

Thin people can put themselves first.

For five years, Anne Fletcher, a registered dietitian and the author of Thin for Life (Houghton Mifflin, $15, amazon.com), worked in an obesity clinic. “So often the women I saw were people who refused to take time for themselves,” she recalls. “Their whole lives were spent giving, giving, giving―which women tend to do anyway, but it was really to a fault. Sometimes you need to put yourself first.”

Thin women prioritize eating right, exercising regularly, and reducing stress―all of which are conducive to staying slim. Fletcher confesses to missing the occasional Little League game to work out but contends that such behavior shouldn’t induce guilt. Rather, it’s about taking care of yourself.

“When people take the reins, they realize that the solution to weight control is inside them, not in some magic potion or fad diet that their mother or sister is on.”

Thin people have thin parents.

And genes are only partially responsible.

“Perhaps 30 percent of being thin is genetic―the rest is environment,” says James O. Hill, Ph.D., director of the Center for Human Nutrition at the University of Colorado Health Sciences Center, in Denver, and cofounder of the NWCR. If you’re raised playing sports and eating healthy, unprocessed foods, chances are you’ll continue those habits into adulthood, significantly raising your odds of staying slim.

Holly Johnson, age 45, a co-owner of a Sarasota, Florida–based marketing and public-relations firm and the mother of an eight-year-old, describes her father as a “beanpole” and says her mother still weighs “within three pounds of what she did when she married my dad.”

But while genetics were clearly in her favor, Johnson credits healthful home-cooked meals for creating a model of good eating that helps her maintain her weight. “We always had breakfast and dinner together,” she says. “I was brought up with family meals, and now my family sits down every night and lights candles. Dining and healthy eating are important to me.”  

Thin people don’t skip meals.

Slender people don’t drop everything to eat the minute their stomach starts to rumble, but they don’t let themselves get famished, either.

“In my work with over 15,000 patients, the number one behavior that leads people to lose control is skipping meals,” psychologist Stephen Gullo says. Why? Being ravenous makes you much less likely to control impulses to overeat.

Alice O’Neill, a trim 40-year-old playwright in Brooklyn, is quite familiar with this phenomenon. “Skipping meals can be deadly for me, because I do get really hungry and I don’t bear the pain of hunger well,” she says. “And if I’m hungry, I’ll eat anything, and too much of it. Sometimes I use hunger as an excuse to eat things that aren’t good for me, like pizza and French fries.”

Thin people limit their options.

While everyone needs a variety of foods for optimal nutrition, professor of nutrition Barbara Rolls's research shows that the more types of food we have available, the more we tend to eat. It’s related to what’s called “sensory-specific satiety"―meaning our stomachs and appetites will cry “Uncle!” after we eat a lot of pasta, but if dessert is pie à la mode, suddenly we’ll find just enough room to partake.

“What happens during a meal of many different foods or courses is that we experience satiety for each food as we eat it,” says Rolls, who is also the author of The Volumetrics Eating Plan ($16, amazon.com). “But we are still ‘hungry’ for foods we haven’t eaten yet, particularly those that have different tastes, aromas, shapes, textures, and other sensory properties.”

Still, Rolls would never recommend severely limiting the number or types of food in an effort to stay slim. “People should increase the variety of low-calorie-dense foods they eat―such as vegetables, fruit, and soup―to get the nutrients they need,” she says.  

Thin people live in Colorado.

OK, so there are thin people outside Colorado. But there must be something the Centennial State knows: According to data from the Centers for Disease Control and Prevention, Colorado has the highest percentage of people with a normal weight (meaning neither overweight nor obese) in the nation.

And why are there fewer fat Coloradans? “My take is that, traditionally, Colorado has attracted people who value outdoor living and health and wellness more,” says James O. Hill, Ph.D., director of the Center for Human Nutrition at the University of Colorado Health Sciences Center, in Denver, who has lived there for 14 years. “People will take off every Friday because they go to the mountains. They’re willing to prioritize health and wellness.”

The state has the country’s largest system of city parks, more than 3 million acres of national parks and forests, 10 major ski resorts, and 400 mountain-biking trails. In addition, 20 percent of Coloradans belong to health clubs―the second-highest percentage in the United States. (Delaware has the highest.) Colorado’s weather also helps. Says Hill: “We have 300-plus days each year when it’s nice to be outside.”

Thin people don’t sit still.

At the Endocrine Research Unit of the Mayo Clinic, in Rochester, Minnesota, a study of 20 self-proclaimed couch potatoes―half of whom were lean, half mildly obese―revealed that the thin volunteers were more likely to stand, walk, and fidget. The researchers noted that the obese participants sat, on average, more than two hours longer every day than the lean ones did.

“If the obese subjects took on the activity levels of the lean volunteers, they could burn through about 350 calories more a day without working out,” says endocrinologist James Levine, the lead author of the study. “Over a year, this alone could result in a weight loss of approximately 30 pounds, if calorie intake remained the same.”

Simply moving around more, taking walks during the workday, and parking your car at the far end of the parking lot can burn many calories. But regular exercise is important, too. “Ninety percent of people who maintain their weight are exercising in a way that’s the equivalent of walking four miles a day,” says registered dietitian Elizabeth Somer, the author of 10 Habits That Mess Up a Woman’s Diet (McGraw-Hill, $17, amazon.com).

Johnson, for instance, does “some yoga stretching and light weights in the morning.” Then, she says, “I combine a run with walking my son to the bus. I’ll usually get some aerobic exercise every day.”

Regular workouts have another dividend: “Exercise makes you more aware of your body,” psychologist Stephen Gullo says. “You’re less likely to eat the chocolate cake that you know will take hours to burn off on the treadmill.”  

Thin people weigh themselves.

For years diet experts discouraged stepping on the scale to keep weight in check. Yet one of the findings of the NWCR is that slim people do weigh themselves regularly. Not obsessively, not agonizing down to the ounce, but at least a couple of times a week. “At the first sign of weight gain, they go right back to their weight-loss plan,” says registered dietitian Elizabeth Somer.

Anne Fletcher, also a registered dietitian, says of the weight maintainers she’s interviewed over the years, “Most have found that it’s easier to manage their weight if they don’t allow themselves to go over their goal.”

Holly Johnson, age 45, a co-owner of a Sarasota, Florida–based marketing and public-relations firm and the mother of an eight-year-old, confirms their findings. She always knows whether she’s in her preferred range of 105 to 113, because she weighs herself about twice a week. “If the scale starts creeping up to the higher end or I feel that things are starting to get out of control,” she says, “I cut back on starchy carbs and dessert.”

Thin people don’t skip breakfast.

You’ve heard it ad nauseam: Breakfast is the most important meal of the day. It’s also a way to stay svelte.

A 2002 study of nearly 3,000 NWCR participants found that 78 percent ate breakfast every day; just 4 percent said they never ate breakfast. (The registry also found that people who don’t eat breakfast have caloric intakes similar to those who do, meaning the skippers make up the calories later.)

A recent study of breakfast eaters in the Journal of the American Dietetic Association backed up other findings that people who eat breakfast are less likely to be overweight than those who don’t.  

Thin people enjoy their food.

It’s tempting to think that one of the reasons thin people stay that way is that they simply aren’t “foodies.” Not true, psychologist Stephen Gullo says. “Naturally thin people enjoy their food every bit as much as overweight people do,” he says. “In fact, many enjoy it more, because they eat without self-reproach.”

Feelings of guilt, or believing that everyone is watching what you’re eating (and thinking you shouldn’t be having that hot-fudge sundae), interfere with enjoyment. “Thin people are selective gourmets,” Gullo says. “Our bodies have a budget, like our checkbook. We should ‘spend’ on what we eat selectively, not compulsively.”

Thin people practice early intervention.

“A large number of the people who seem to be ‘naturally’ thin have evolved their own strategies for staying that way,” psychologist Stephen Gullo says. They have to, because thin people do gain weight. But they take action when the numbers on the scale creep up or their pants become hard to button.Their response usually involves a combination of exercise and dietary changes.

Carla Matthews, a 38-year-old stay-at-home mother of two in Newport Beach, California, says that when she goes over her upper limit of 130 pounds, she cuts out dessert and wine, drinks more water, and rides her exercise bike three times a week instead of once (in addition to doing Pilates twice a week). “I also tend to eat more salads and do my ‘halves’ routine, where I only eat half of whatever I would normally,” she says. “After 7 to 10 days, my weight is usually back in the comfort zone.”

Understanding what causes you to put on pounds can go a long way toward preventing them. “Thin people know they need to either limit exposure to certain foods that trigger appetite or limit the quantity or frequency of those foods,” says Gullo, whose personal kryptonite is pizza. “Or, if they can’t do any of those, they ban the food completely.”

Anne Casher, a 37-year-old stay-at-home mother of two in Wilton, Connecticut, has learned to steer clear of her enemy: “I decided not to keep ice cream or cookies in the house,” she says, “because if there are some really good chocolate-chip cookies in the drawer, I’m inclined to eat them after dinner even if I’m not hungry.”

Because stress, sadness, anger, loneliness, and grief can send anyone to seek solace in a pint of Ben & Jerry’s, the successfully thin person knows mood-driven eating when she sees it and defends against it, Gullo adds. “Thin people recognize the syndrome and don’t bring trigger foods into the place where it happens,” he says. “Mood eating takes place primarily at home.”  

Thin people do what works.

Perhaps nowhere does the frequently cited definition of insanity―doing the same thing over and over and expecting a different result―apply more aptly than with weight loss. The math makes this clear: By one estimate, one-third of Americans are on a diet, but 64 percent of us remain overweight or obese. Something doesn’t add up.

The biggest difference between the permanently thin and everyone else might very well be this: Those who don’t gain (or regain) have come up with effective, specific, and often personal ways to keep their weight in check.

Becky Grebosky, age 38, a children’s-clothing and gift manufacturer and a mother of two in Albuquerque, New Mexico, makes a smoothie when she feels like having a treat. “I mix up yogurt, a bit of juice, some water, ice, and whatever fruit is around,” she says. “It tastes like a milk shake.” Other thin people can’t live without dessert, so they shave calories elsewhere or “pay” for the indulgence with extra time or intensity at the gym. “Thin people get out of the mind-set of being ‘good’ or ‘bad,’” psychologist Stephen Gullo says. “It’s about doing what works.”

This practice may account for the single most annoying trait of the always-thin: that their achievement seems effortless. But it’s not. “People think you never have a fat day―I do,” Holly Johnson, age 45, a co-owner of a Sarasota, Florida–based marketing and public-relations firm and the mother of an eight-year-old, says. “I have days when I feel awful. But I spend a lot of time and energy on fitness and cooking. And I have to work really hard, especially now that I’m over 40.”

But when good habits are integrated into your life, something shifts. There’s no need to count calories, agonize over an order of fries, track miles walked, or (worst of all) talk endlessly about what you’re eating and not eating. For the thin, feeling strong, healthy, and, yes, slim are powerful rewards―and their chief motivation to continue, as Anne Fletcher, a registered dietitian, has heard from dozens of people. “More than 90 percent of those who have mastered weight maintenance feel like they’re not dieting,” she says. “It becomes a way of life.”