(CNN) What are the magic words to use when a loved one's weight is rising dangerously high? Unfortunately, there are none.
"You're not telling anyone something they don't know," warned Ed Abramson, a psychologist and professor at California State University.
Most people are undoubtedly aware of their own appearance and have also read at least one of the many reports about the dangers of excess weight, he added. After all, it's no longer news that more than one-third of adults in the United States are obese -- meaning a body mass index of 30 or more. And plenty of research shows the negative health effects of excess weight, including type 2 diabetes, heart disease, some cancers and difficult physical functioning, according to the Centers for Disease Control and Prevention.
Most people who feel that their weight is unhealthy have already tried to diet, said Abramson, so any conversation about their weight will probably come across as nagging, and this will just increase their shame, defensiveness and even secretiveness. Talking about it, you might worsen the problem, he explained.
Still, the problem remains: You're worried. So, do you say something or say nothing?
According to Dr. Barbara Berkeley, a board-certified physician in both internal and obesity medicine, it's impossible to not intervene in other people's lives. "Everybody does it, so the question is how to do it effectively," she said.
Since people don't lose weight or change their habits unless they want to, you must first recognize that you can only inspire them so much. Really, it's up to them.
A variety of factors contribute to gaining weight these days, Abramson explained. We eat bigger portions of calorie-dense foods and we eat out at restaurants serving too-salty meals. Meanwhile, many of us work jobs that do not involve any real physical effort and drive cars instead of walking. There's also the issue of the food itself.
"So we've been doing research on the overlap of food and drug addiction," said Nicole Avena, a research neuroscientist, explaining how recent studies have shown similar addiction-like responses to food -- bingeing, tolerance, craving, withdrawal -- and similar changes occurring in the brain within the dopamine system (pleasure center) in the brain.
Here's the catch: These "junky" responses do not occur with just any food -- you're not likely to binge on, say, grilled salmon. It's only highly processed foods that inspire this reaction.
"The level of processing was the highest indicator of whether or not the food was addictive," said Avena, author of "Why Diets Fail." She believes that simply "hearing this information" could change the conversation and even be empowering for some people, helping them to avoid potentially "addictive" foods altogether.
However, not everyone is convinced by the evidence, noted Abramson. While many scientists support Avena's view that certain foods can inspire addiction, other scientists acknowledge that certain foods may result in atypical physiological changes but that doesn't equate to the dependence and cravings aroused by drugs.
Before you start a conversation about someone else's presumably "unhealthy" food habits, you need to understand what a too-high number on the scale means to the other person --- and also to you, said Bryan Karazsia, an assistant professor of psychology at the College of Wooster. The focus needs to be about health and behavior, not weight, and definitely never about appearance.
You also need to reflect on how weight and food have been talked about over the years.
"It's not all about that one conversation," said Karazsia.
So, if you're a parent who wants to help a child -- even a young adult child, but especially teens -- Berkeley suggests modeling the behavior you want to see. You, yourself, must walk the walk by cutting sugar and processed foods out of your diet while taking up exercise. This is based on the "very obvious generalization" that children accept the values of the family, said Berkeley. Most of us become like our parents.
With other family members, it may not matter so much whether they are a sister, brother or parent, it is the fact that they are adults or older that matters most. Here, you need to begin any discussion of weight by understanding how they feel, said Berkeley. "You have to tread very carefully," she explained, since you're touching their self-esteem.
People know they are overweight, she emphasized, they just feel unable to do anything about it: "Say you were really bad at math and yet you were in a class of math geniuses ... it's like that."
Because it feels just like that, the most important thing you need to do is take the onus on yourself by saying things like, "I really love you, and I don't want to lose you," or "I feel we're not as healthy as we could be, so when you're ready, I'll help you," said Berkeley.
Essentially, you need to offer a hand and a prepared plan in which you become a partner and set a challenge to take on together, said Berkeley. And then, you must give them time to decide whether they want to accept.
Timing is critical. If a person is going through a rough time, a divorce, say, or some setback, that may not be the right moment to address a weight problem and set a challenge, said Berkeley.
"Frequently, what will happen is, someone overweight will make a comment like, 'I shouldn't have had a hot fudge sundae' or 'I'm out of breath,' " said Abramson, author of "Emotional Eating: What You Need to Know Before Starting Your Next Diet."
By making some reference to their weight, he suggested, they've opened the conversational door -- by a crack. To enter, you need to say something like, "Is there anything I can do to help you with your diet?"
"There's always that guy who has lost a lot of weight and now he thinks he's an expert," said Dr. Arya M. Sharma, a professor at University of Alberta in Canada. Surviving cancer doesn't make you an oncologist, and losing weight doesn't make you an obesity expert, he noted.
"Usually, I would say health advice should come from health professionals," Sharma said, explaining that he understands the concerns people might have seeing a loved one who appears overweight and unhealthy. Still, it's really not their place to give advice, other than suggesting a person see their doctor.
In fact, Sharma said, this is the same advice you should heed yourself if you're worried about your own weight.
This question of when to intervene is a tricky business and Sharma, as a doctor, adheres to the World Health Organization's standard: "Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health."
There's not a lot of information in BMI, it's just a measure of height and weight that may be good for looking at the entire population or screening, but as a doctor, he's had to answer questions like: Who do you prescribe obesity surgery or a behavioral intervention?
He developed a tool for deciding who needs treatment and who does not. Basically, his Edmonton Obesity Staging System provides doctors with other criteria and standards in order to help them figure out whether a patient is "healthy fat" or just overweight.
That's part of why it's important to involve a doctor in the conversation. BMI, the guide most of us use, doesn't tell you everything you need to know.
"You can have a body mass index of, say, 35, where you've got high blood pressure, you're pre-diabetic, you've got arthritis and sleep apnea," Sharma explained. "Or you can have a BMI of 35, and you have none of those problems."
"We focus too much on weight loss," Berkeley said, adding that any diet program in the world is just starving. To keep the weight off and to stay healthy, most people need to be detoxed from the sugars and foods that immediately turn into sugar in the blood (such as pasta and bread), which can act like addictive substances in the brain, Berkeley explained.
The reason some people gain weight easily is because of defective insulin function, said Berkeley. Insulin, a hormone, helps your body use sugar. Meanwhile, our world is awash in insulin-stimulating food: sugary and starchy foods, which provide our bodies with hormonal encouragement to gain weight or regain lost weight.
To keep off the weight, you not only need a new way of eating healthy, "you have to believe in it," said Berkeley, who wrote "Refuse to Regain: 12 Tough Rules to Maintain the Body You've Earned." After all, it will be hard avoiding foods your body craves after being starved. However, Berkeley points out, there are plenty of vegetarians living in a world filled with meat --- they've developed "a food constitution" and do not deviate from that.
Meanwhile, there needs to be more widespread understanding that a diversity of bodies, some more or less slender, not only exist but they all can be healthy. "I am all for body diversity and body acceptance," Karazsia said.
Why do we fat-shame or make sweeping conclusions about which bodies are "better" than others, when scientists have acknowledged that a little bit of body fat can be healthier for some people than too little body fat?
"If we just focus on weight, we end up with weight being the outcome," said Karazsia, explaining that the scale might not change at all. A person might lose fat and gain muscle but not change their actual weight -- but by eating differently, exercising more, they become mentally and physically healthier. "I would just encourage a lot of people to look at things in a different way."
In fact, there's a significant genetic component to how much each of us weighs, according to Abramson, and when it comes to those who appear attractively thin, some people have simply won "the genetic lottery," he said. "The emphasis on slenderness is overdone."
While Berkeley doesn't "accept being lured in by food and then saying 'I should accept that I am overweight,' " she does believe that there is no one size fits all when it comes to a healthy weight. As long as you are a size where you can do what you want to do physically and you can maintain it, "you're perfectly fine," said Berkeley.