Obesity is a national health crisis—that much we know. If current trends continue, it will soon surpass smoking in the U.S. as the biggest single factor in early death, reduced quality of life and increased health care costs. A third of adults in the U.S. are obese, according to the Centers for Disease Control and Prevention, and another third are overweight, with Americans getting fatter every year. Obesity is responsible for more than 160,000 “excess” deaths a year, according to a study in the Journal of the American Medical Association. The average obese person costs society more than $7,000 a year in lost productivity and extra medical treatment, say researchers at George Washington University. Lifetime-added medical costs alone for a person 70 pounds or more overweight amount to as much as $30,000, depending on race and gender.

All this lends urgency to the question: Why are extra pounds so difficult to shed and keep off? It does not seem as though it should be so hard. The basic formula for weight loss is simple and widely known: consume fewer calories than you expend. And yet if it really were easy, obesity would not be the nation's number-one lifestyle-related health concern. For a species that evolved to consume energy-dense foods in an environment where famine was a constant threat, losing weight and staying trimmer in a modern world of plenty fueled by marketing messages and cheap empty calories is, in fact, terrifically difficult. Almost everybody who tries to diet seems to fail in the long run—a review in 2007 by the American Psychological Association of 31 diet studies found that as many as two thirds of dieters end up two years later weighing more than they did before their diet.

Science has trained its big guns on the problem. The National Institutes of Health has been spending more than $800 million a year on studies to understand the metabolic, genetic and neurological foundations of obesity. In its strategic plan for funding obesity research, published in 2011, the NIH placed at the top of the list of research opportunities the investigation of basic biological processes related to obesity, including “specific roles of organs, tissues, and molecules in the development of obesity” and “genes, epigenetics, and critical periods in human development.”

This research has provided important insights into the ways proteins interact in our body to extract and distribute energy from food and produce and store fat; how our brain tells us we are hungry; why some of us seem to have been born more likely to be obese than others; and whether exposure to certain foods and toxic substances might modify and mitigate some of these factors. The work has also given pharmaceutical companies numerous potential targets for drug development. What the research has not done, unfortunately, is make a dent in solving the national epidemic.

Maybe someday biology will provide us with a pill that readjusts our metabolism so we burn more calories or resets our built-in cravings so we prefer broccoli to burgers. But until then, the best approach may simply be to build on reliable behavioral-psychology methods developed over 50 years and proved to work in hundreds of studies. These tried-and-true techniques, which are being refined with new research that should make them more effective with a wider range of individuals, are gaining attention. As the NIH puts it in its proposed strategic plan for obesity research: “Research findings are yielding new and important insights about social and behavioral factors that influence diet, physical activity, and sedentary behavior.”

How we got here
the desperation of the obese and overweight is reflected in the steady stream of advice pouring daily from sources as disparate as peer-reviewed scientific journals, best-selling books, newspapers and blogs. Our appetite for any diet twist or gimmick that will take the pounds off quickly and for good seems to be as insatiable as our appetite for the rich food that puts the pounds on. We, the public, love to believe in neat fixes, and the media oblige by playing up new scientific findings in headline after headline as if they are solutions.

It does not help that the scientific findings on which these headlines are based sometimes appear to conflict. For example, a 2010 study in the American Journal of Clinical Nutrition linked weight loss to increased dairy intake, although a 2008 meta-analysis in Nutrition Reviews found no such link. A 2010 paper in the Journal of Occupational and Environmental Medicine postulated a connection between job stress and obesity, but another report that year in the journal Obesity concluded the two are uncorrelated. Part of the problem is that obesity researchers are in some ways akin to the metaphorical blind men groping at different parts of the elephant: their individual study findings address only narrow pieces of a complex puzzle.

When the research is taken together, it is clear that the obesity fix cannot be boiled down to eating certains kinds of food or taking other simple actions. Many factors contribute to the problem. Some are environmental—the eating habits of your friends, what food is most available in your home and your local stores, how much opportunity you have to move around at work. Others are biological, such as genetic predispositions for storing fat, having higher satiety thresholds or having more sensitive taste buds. Economics and marketing play roles, too. Junk food is much cheaper than fresh produce. And food companies are masters at manipulating our social nature and our evolutionary “programming” to steer us toward unhealthy but profitable fare. That is why the narrow “eat this” kinds of solutions, like all simple solutions, fail.

When we go on diets and exercise regimens, we rely on willpower to overcome all these pushes to overeat relative to our activity level. And we count on the reward of getting trimmer and fitter to keep us on the wagon. It is rewarding to lose the weight, of course. Unfortunately, time works against us. As the weight comes off, we get hungrier and develop stronger cravings and become more annoyed by the exercise. Meanwhile the weight loss inevitably slows as our metabolism tries to compensate for this deprivation by becoming more parsimonious with calories. Thus, the punishment for sticking to our regimen becomes increasingly severe and constant, and the expected reward recedes into the future. “That gap between the reinforcement of eating and the reinforcement of maybe losing weight months later is a huge challenge,” says SungWoo Kahng, a neurobehaviorist who studies obesity at the University of Missouri.

We would be more likely to stick with the regimen if it remained less punishing and more reliably rewarding. Is there a way to make that happen?

From biology to brain
The most successful way to date to lose at least modest amounts of weight and keep it off with diet and exercise employs programs that focus on changing behavior. The behavioral approach, tested over decades, involves making many small, sustainable adjustments in eating and exercise habits that are prompted and encouraged by the people and the rest of the environment around us.

The research in support of behavioral weight-loss approaches extends back more than half a century to Harvard University psychologist B. F. Skinner's development of the science of behavioral analysis. The field is founded on the notion that scientists cannot really know what is going on inside a person's brain—after all, even functional MRIs, the state of the art for peering into the mind, are crude, highly interpretable proxies for cognition and emotion that reduce the detailed firing of billions of neurons in complex circuits to a few blobs of color. But researchers can objectively and reproducibly observe and measure physical behavior and the immediate environment in which the behavior occurs, allowing them to identify links between environment and behavior. That typically includes trying to spot events or situations that may be prompting or triggering certain behaviors and noting what may be rewarding and thus reinforcing of some behaviors or punishing and thus inhibiting of others.

The effectiveness of behavioral interventions has been extensively documented for many disorders and problem behaviors. A 2009 meta-analysis in the Journal of Clinical Child & Adolescent Psychology concluded that “early intensive behavioral intervention should be an intervention of choice for children with autism.” A systematic review sponsored by the U.S. Preventive Services Task Force concluded that even brief behavioral-counseling interventions reduced the number of drinks taken by problem drinkers by 13 to 34 percent for as long as four years. Studies have found behavioral-intervention successes in challenges as diverse as reducing stuttering, increasing athletic performance and improving employee productivity.

To combat obesity, behavioral analysts examine related environmental influences. Which external factors prompt people to overeat or to eat junk food, and which tend to encourage healthful eating? In what situations are the behaviors and comments of others affecting unhealthful eating? What seems to effectively reward eating healthfully over the long term? What reinforces being active? Behaviorally focused studies of obesity and diets as early as the 1960s recognized some basic conditions that seemed correlated with a greater chance of losing weight and keeping it off: rigorously measuring and recording calories, exercise and weight; making modest, gradual changes rather than severe ones; eating balanced diets that go easy on fats and sugar rather than dropping major food groups; setting clear, modest goals; focusing on lifelong habits rather than short-term diets; and especially attending groups where dieters could receive encouragement to stick with their efforts and praise for having done so.

If these strategies today sound like well-worn, commonsense advice, it is because they have been popularized since 1963 by Weight Watchers, which was founded to provide support groups for dieters. Weight Watchers later added other approaches and advice in keeping with the findings of behavioral studies and billed itself as a “behavior-modification” program. “Whatever the details are of how you lose weight, the magic in the sauce is always going to be changing behavior,” says Karen Miller-Kovach, former chief science officer of Weight Watchers. “Doing that is a learnable skill.”

Studies back the behavioral approach to weight loss. A 2003 review commissioned by the U.S. Department of Health and Human Services found that “counseling and behavioral interventions showed small to moderate degrees of weight loss sustained over at least one year”—a year being an eon in the world of weight loss. An analysis of eight popular weight-loss programs published in 2005 in the Annals of Internal Medicine found Weight Watchers (then in its pre-2010 points-overhaul incarnation) to be the only effective program, enabling an average reduction of 3 percent body weight maintained for the two years of the study. Meanwhile a 2005 JAMA study found that Weight Watchers, along with the Zone diet (which similarly recommends a balanced diet of protein, carbohydrates and fat), achieved the highest percentage (65 percent) of one-year diet adherence among several popular diets, noting that “adherence level rather than diet type was the key determinant of clinical benefits.” A 2010 study in the Journal of Pediatrics found that overweight children receiving one year of behavioral therapy dropped 1.9 to 3.3 units more in body mass index, a height-weight relation correlated to body fat, than control subjects did. The Pediatrics report noted that “more limited evidence suggests that these improvements can be maintained over the 12 months after the end of treatments.”

A 2010 study in Obesity found that continuing members of Take Off Pounds Sensibly (TOPS), a national, nonprofit, behaviorally focused weight-loss organization, maintained a weight loss of 5 to 7 percent of their body weight for the three years of the investigation. The U.K.'s Medical Research Council declared in 2010 that its own long-term study had shown that programs based on behavioral principles are more likely to help people take and keep the weight off than other approaches. (The study was funded by Weight Watchers, but without its participation.)

Weight Watchers and other widely marketed programs tend to fall short, however, in enlisting a full range of behavioral techniques and customizing them to meet the varied needs of individuals. They do not routinely provide individual counseling, adapt their advice to specific challenges, assess environmental factors in a member's home, workplace or community, provide much outreach to members who do not come to meetings, or prevent their members from shooting for fast, dramatic, short-term weight loss or from restricting food groups. In search of profits, Weight Watchers sometimes even mildly panders to these self-defeating notions in its marketing. “Some people join us to drop 10 pounds for a high school reunion,” Miller-Kovach says. “They achieve that goal, then stop coming.”

To close that gap, a number of researchers have turned their attention in recent years to improving, expanding and tailoring behavioral techniques, with encouraging results. For example, Michael Cameron, chief clinical officer of Pacific Child & Family Associates, a national group of clinics for children with special needs, has authored more than 20 articles in peer-reviewed journals documenting the effectiveness of a wide range of behavioral interventions. A former faculty member at Harvard Medical School's teaching psychiatric hospital, Cameron in 2011 conducted a yearlong, four-person study—behavioral analysts generally do very small group or even single-subject studies to more closely tailor the intervention and observe individual effects—in which the subjects met together with him via online videoconferencing for reinforcement, weighed themselves on scales that transmitted results via wireless networks, and had their diets optimized to both reduce caloric density and address individual food preferences. Favorite foods were used as a reward for exercise. The subjects lost 8 to 20 percent of their body weight, and Cameron says they and the several other people he has worked with outside the study have all kept the weight off.

Matt Normand, a behavioral analyst at the University of the Pacific, has investigated ways to more precisely track subjects' calorie intake and expenditure. He collects receipts of their food purchases, provides checklists to record what they eat, and uses pedometers and other devices to measure their physical activity. He then gives participants daily detailed accounts of their calorie flow. In one published study, Normand showed that three of four subjects reduced calorie intake to recommended levels.

Richard Fleming, a researcher at the University of Massachusetts Medical School's Shriver Center, has in Obesity looked at ways to encourage parents to steer their children to healthier choices. He has found, among other techniques, that showing parents in person what appropriate serving sizes of foods look like on plates is helpful. Another successful Fleming trick: letting children pick out a small treat at a food store—as long as they walk there. “Kids can really respond to that reward for being active,” he says.

Why are behavioral interventions effective? Laurette Dubé, a lifestyle psychology and marketing researcher at McGill University's Faculty of Management, notes that our environment is currently one in which ubiquitous, sophisticated marketing efforts prey on our need for sensory gratification as well as our vulnerability to misinformation. In addition, the poor eating and exercise habits we observe in our friends, family and colleagues encourage us to follow suit. In essence, behavioral interventions seek to reconfigure this environment into one in which our needs for information, gratification and social encouragement are tapped to pull us toward healthy food and exercise choices rather than away from them. “When we are getting the right messages in enough ways, we have a better chance of resisting the urge to eat more than we need,” Dubé says.

Changing policy
There is no one-size-fits-all solution, behavioral or otherwise, to the problem of obesity. But although behavioral interventions work best when they are customized to individuals, mass-market behavioral approaches such as TOPS and Weight Watchers are at least fairly effective. Why don't more people lose weight with them? The main reason is that people simply do not sign up for them, often because would-be weight losers are chasing fad diets or supplements or have read that obesity is locked into our genes. Weight Watchers, by far the most popular behavioral weight-loss program, counts only 600,000 meeting-attending members in its ranks in North America. That means that in the U.S., fewer than one out of 100 obese people and about one out of 200 overweight people are part of a formal behavioral-modification program.

Public policy may be changing, however. The U.S. Surgeon General's office and the CDC have both publicly lined up behind behavioral approaches as the main weapon in what is becoming a war on obesity. First Lady Michelle Obama's Let's Move campaign against childhood obesity consists almost entirely of finding ways to encourage children to eat lower-calorie foods, to become more active, and to enjoy doing it. San Francisco's 2010 ban of free toys in fast-food meals for kids suggests that more officials may be ready to pressure the food industry into easing up on what are essentially obesity-supportive marketing tactics. To encourage people in poorer, disproportionately overweight communities to buy healthier food, the White House has proposed subsidizing the costs of fruits and vegetables.

Approaching the problem from the other direction, former New York City mayor Michael Bloomberg advocated modifying food-assistance programs to restrict the purchase of high-sugar beverages and supported a ban, passed by the city's board of health, on extra-large servings of sugary sodas. In 2014 voters in Berkeley, Calif., approved a surtax of 1 cent per ounce on such drinks. New York City has also offered vouchers for buying produce at farmers' markets to low-income families and incentives to stores to offer healthier fare.

Increasing access to behavior therapy would help, too. Many overweight people might need only online behavioral monitoring, support and progress-sharing tools, which have proved moderately effective in studies. Others may need much more intensive, more personal interventions of the kind Cameron is developing. Given that obesity especially plagues the economically disadvantaged, fees for these programs may have to be heavily subsidized by the government and health care insurers. A weekly session with a behavioral therapist costing $50 would amount to $2,500 a year, or a bit more than a third of the $7,000 a year societal and medical costs of obesity—and the sessions might be needed for only a year or two to establish new, permanent eating and exercise habits, whereas the savings would continue on for a lifetime.

It is too soon to say whether the public will accept government efforts to push it toward healthier choices. San Francisco's ban on Happy Meal toys was initially vetoed by the mayor in response to angry reaction. Efforts by Let's Move to bring healthier food to school cafeterias have been intensely criticized by some as overly intrusive. The courts threw out New York City's ban on large sodas. And voters have rejected taxes on high-calorie beverages in San Francisco and most other cities and states that have proposed them.

Even if such efforts are eventually fully implemented nationwide, there is no way of being sure they will significantly reduce obesity. The current rate of obesity is far beyond any ever seen before on the planet, and thus a large-scale solution will necessarily be an experiment in mass behavior change. But the research suggests that such a grand experiment would be our best shot at fixing obesity and that there is reason to be hopeful it will succeed. Given that more and more scientists, public policy experts and government officials seem eager to get it off the ground, we may well have early findings within this decade.