(CNN) Diet is "a four-letter word for failure," if you ask Teena Henson .

In the past, the 57-year-old Gilmer, Texas, resident would try fad diets that did nothing but leave her feeling frustrated, she said.

"There was one called a grapefruit diet or something where you didn't eat anything but grapefruit," Henson said. "If you do something like that, that's what I meant by 'diet' being a failure."

She didn't consistently exercise, either. Although she didn't have any serious health conditions, she knew that her lifestyle was killing her. Henson was 5-foot-4 and 332 pounds.

Then, about six years ago, Henson was listening to the radio when an ad for Anytime Fitness blasted through the speakers. She said a quick prayer: "God, I wish we had one of those here."

Two weeks later, a gym opened in her neighborhood.

"I looked at it as an answered prayer," Henson said. "If that hadn't happened, there's a possibility I could have died or have any of the conditions associated with being obese. There's a history of heart disease and diabetes in my family. I was headed in that direction, and I didn't want to go there."

Photos: Why a Western diet could be bad for you Photos: Why a Western diet could be bad for you The Western diet is spreading across the world. It's characterized by a high intake of red meat, refined sugars and saturated fat -- but little fiber. Hide Caption 1 of 9 Photos: Why a Western diet could be bad for you A common feature of Western diets is processed fast food. Here's a pepperoni pizza high in fat and carbohydrates and topped with cured, processed meat. Hide Caption 2 of 9 Photos: Why a Western diet could be bad for you Candy bars have been highlighted as a key example of processed foods. Ingredients such as fructose and palmitic acid may initiate a low-level immune response in the body, distracting the immune system from other infections. Hide Caption 3 of 9 Photos: Why a Western diet could be bad for you

Some studies have linked eating too much red meat with a shortened life span Hide Caption 4 of 9 Photos: Why a Western diet could be bad for you Sugary drinks are the epitome of the fast-food diet. Their high sugar content increases the likelihood of obesity, diabetes and other health conditions. Hide Caption 5 of 9 Photos: Why a Western diet could be bad for you The Mediterranean diet is renowned for its health benefits. It contains low levels of red meat, sugar and saturated fats and is high in fish and unsaturated fats such as olive oil, fruits, vegetables and legumes. Hide Caption 6 of 9 Photos: Why a Western diet could be bad for you Diets with little fruit and vegetables can be low in vitamins, minerals and fiber crucial to growth and health. Hide Caption 7 of 9 Photos: Why a Western diet could be bad for you The Japanese diet is also known for its healthy components -- high in soy protein and vegetables. Hide Caption 8 of 9 Photos: Why a Western diet could be bad for you Diets on the southern Japanese Okinawa Islands contain large amounts of fish, whole grains, soy protein and vegetables. Hide Caption 9 of 9

Ever since, Henson has been going to the gym daily with two of her friends and has been preparing healthier meals for herself. She has lost 175 pounds -- more than 50% of her previous body weight -- and she is keeping the weight off, she said. She has ditched fad diets and avoids placing too much emphasis on how much she weighs and instead focuses on how she feels.

But she remembers how easy it was to stick to the same old foods and avoid exercising, and how hard it was to find a healthier routine that led to long-term weight loss.

Across the United States, obesity rates are rising. But fewer Americans are trying to lose weight, according to a paper published in the journal JAMA last month.

Experts are now trying to figure out why: whether it's because they don't realize they're at an unhealthy weight, because weight loss is hard or something else entirely.

'I can't sit in judgment'

Before her weight loss, Henson was just like the more than one-third of American adults who meet the criteria for obesity, as their body mass indexes are 30 or higher, according to the Centers for Disease Control and Prevention

More than two in three American adults are considered to be obese or overweight , with body mass indexes 25 and higher.

The new paper showed that more than 30% of Americans said they were obese in 2015, compared with about 19% in 1997. Of those who were overweight or obese, about 49% said they were trying to lose weight in 2014, compared with about 55% in 1994.

"I've pondered that several times, as to why some people would want to be unhealthy when they can be healthy, but there are so many variables in someone's life that you don't know about," Henson said.

"I can't sit in judgment as to why that person wants to or doesn't want to. I just know what I needed and what I needed to do to change," she said. "You can't change what you've tried in the past, but you can set your sights for a better future.

"Everyone's on a different path, a different journey," Henson said.

Is there a 'new normal'?

As obesity rates have increased, what many people perceive as "overweight" or a "normal weight" has shifted , said Dr. Jian Zhang, an associate professor at Georgia Southern University's College of Public Health and lead author of the new paper.

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In previous research, Zhang and his colleagues found that more overweight or obese adolescents incorrectly believed that their body weights were "just fine," compared with adolescents in the late 1980s and early 1990s.

For the new paper, "we hypothesized that the prevalent misperception may lead to a lack of motivation to lose weight. The current study just provides the missing piece of the puzzle," Zhang said.

"We are stuck in a vicious cycle. More people are getting obese; more are fine with their weight; when they are looking around, they find more persons with even larger bodies, and more are getting less motivated to lose weight, and in turn, we are getting even heavier," he said.

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Dr. Randy Rockney, a pediatrician at Hasbro Children's Hospital in Providence, Rhode Island, has noticed the same thing happening among children, he said.

"Increasing obesity and overweight trends probably result in 'new normals,' " said Rockney, who was not involved in the new paper.

"Looking at society in general, overweight and obese people are less likely to perceive themselves as aberrant," he said. "It's really hard to lose weight, but it's not impossible, and I think there are a lot of people who have given up."

Rockney, 63, knows those challenges too well.

A pediatrician and his weight struggles

Rockney has always been an avid exerciser, as well as a foodie. He has never been obese but often falls within the overweight category , he said.

Standing at 6-foot-1, Rockney said his weight has fluctuated since he was in medical school, from the mid-180s to a high of 218, which meets the criteria for "overweight."

Rockney never really made an effort to closely monitor his weight or lose pounds until well into his 50s, he said. That's when his blood-sugar levels started creeping up, a sign of prediabetes

"The numbers are very sensitive to my weight," he said of his blood-sugar levels. "If I go up by five pounds, it will change the numbers adversely, and then, conversely, losing five pounds makes a significant improvement."

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So Rockney decided to enroll in a weight loss study at work. He began calculating and restricting his fat and calorie intake, recording the foods and drinks he consumed, and weighing himself. He dropped to 193 pounds.

The weight loss was tough but not impossible, Rockney said. "I am more weight conscientious than I was, particularly regarding diet. I regained some of the weight I lost but remain well under where I started."

He said he currently weighs about 203 pounds, which technically still places his body mass index in the overweight category.

"A lot of physicians are conscious of this, that it's hard to preach healthy diet and exercise and healthy weight if you as a physician are not at a healthy weight," he said. "Among my patients and their families, excess weight continues to be a very common problem. We try to help them, but it can be challenging."

'It's painful. It's hard to drop pounds'

The new paper in JAMA included data on 27,350 overweight and obese adults who reported whether they were trying to lose weight between 1988 and 1994, 1999 and 2004, and 2009 and 2014.

The data, which were based on self-reports, came from the National Health and Nutrition Examination Survey

"It's unfortunate that the current study was based on interviews rather than direct observation," Zhang said. "This is the reason we cannot rule out the possibility that many adults are actually fully engaging with a healthy lifestyle, but not on purpose to lose weight."

He added that the data did not include reports from the adults as to why they were not trying to lose weight, but he has some theories.

"First and foremost, it's painful. It's hard to drop pounds. Many of us tried and failed, tried and failed, and finally failed to try any more," Zhang said.

The researchers wrote that some overweight people are not trying to lose "due to body weight misperception reducing motivation to engage in weight loss efforts. ... The chronicity of obesity may also contribute. The longer adults live with obesity, the less they may be willing to attempt weight loss, in particular if they had attempted weight loss multiple times without success."

Yet Kelly Brownell, dean of the Sanford School of Public Policy at Duke University and an expert on obesity, said he would come to a different set of conclusions.

Making weight gain prevention a priority

"I think there are other possibilities that might be at least as important. One is that almost everybody who is overweight has tried to lose, and people are recognizing more and more that it's a very difficult challenge," said Brownell, who was not involved in the paper.

"Most approaches to weight loss produce temporary loss. People tend to regain and then go on more diets later, and so some people feel that it's not worth the effort and that the risk of failure is too high," he said. "Most people who are overweight realize that there are negative consequences and would like to lose weight if they could. But they realize that it's a very hard path to go down and that most people are not successful.

"It argues more than ever for the importance of prevention, because once people become overweight, it's very hard to lose, it's even harder to keep the weight off, and therefore preventing the weight gain in the first place has to be a national priority."

The researchers of the new paper, however, also noted that primary care clinicians might not be discussing weight issues with their patients, something that has been found in separate studies.

"We published a (previous) study that found that primary care physician weight-related counseling , comparing rates in 1995-1996 to 2007-2008, significantly declined over this time period to only occurring at 6.2 percent of visits," said Dr. Jennifer Kraschnewski, associate professor at the Penn State College of Medicine, who was not involved in the new paper.

"Further, this decline was greatest in patients with obesity, patients at most need for physician intervention," she said.

The study on weight-related counseling, of which Kraschnewski was a co-author, was published in the journal Medical Care in 2013

"This may be due to a variety of reasons, including physician discomfort with providing counseling, less time available due to increased other patient conditions or even a greater acceptance of higher rates of obesity," she said. "We know that if physicians simply tell their patients they are overweight, they are more likely to be successful in their weight loss efforts. Therefore, it's critical we find a way to help reverse these trends."

However, pediatrician Rockney said he hasn't observed a decline in weight-related counseling in his own professional experience.

"For a long time, I could sense a deep cynicism about addressing the weight problem," he said. "But in recent times, there are a couple of my colleagues who have really taken on the obesity issue with kids and are really pushing intervention."

A weighty and uncomfortable discussion

Before his weight loss, Rockney said, he sometimes felt self-conscious counseling parents and children about losing weight.

In a 2014 essay in the online magazine Pulse , Rockney recalled one instance in which he was counseling a teenage patient.

That patient turned to his mother and Rockney and said, "Hey, I think we all could stand to lose 15 or 20 pounds," making a reference to the doctor's weight.

Now, "I feel more confident in terms of advising families, people, what it is that can work for weight loss," Rockney said.

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He often advises his patients to eat a healthy breakfast daily and monitor their caloric intake for weight loss. For instance, a blueberry muffin can take up about a third of your daily calories, since it has almost 500 calories, he said.

Rockney also advises his patients to weigh themselves daily, as addressing a lapse in weight loss can prevent even more weight gain, he said.

"One important principle I learned and still think to myself is, 'don't let a lapse become a relapse.' That's where regular weighings help, because I can potentially intervene before things get out of hand," Rockney said.

He said his effort to maintain his current weight or even lose weight again continues.

Beyond the clinic walls, having discussions about weight can be even more uncomfortable, Penn State's Kraschnewski said.

"Studies tell us that the vast majority of people who are overweight are interested in losing weight, but interest doesn't necessarily translate to action," she said.

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If a loved one's weight might be putting their health at risk, Kraschnewski offered some advice on how to discuss weight loss.

"Look for opportunities to have a conversation, such as if your loved one makes a comment about their weight. If they aren't happy with their current weight, offer to help them talk to their doctor or look for other weight loss resources in your community," she said.

"Think about ways you could be active together," she said. "Having a partner on the journey to a healthier weight is one of the most effective ways for people to be successful."