A couple of years ago, I wrote a purposely provocative post for the New York Times’ Well blog arguing that it was reasonable for physicians to discuss serious health issues with their patients without first asking permission to do so. Unfortunately, the editors titled the piece, “Can We Talk About Your Weight?” which perhaps implied that the only people in need of such paternalistic directions were those who were overweight (this was not my intention). I have written about many controversial medical topics, including euthanasia, lobotomy, and mammography, but have never been so savaged in a comments section. Readers accused me of being arrogant, thoroughly insensitive to my overweight patients, and blind to the “humanity around me.” One wrote she was “really glad you’re not my doctor.” Doctors like me had no business lecturing their heavy patients about what they should and should not do—as these individuals likely knew more than I did anyway.

Once I got over my defensiveness, I realized that the feelings that had surfaced in the comments revealed an important message about the inaccurate and insensitive remarks that overweight individuals often receive. Many commenters related experiences with physicians in which they were told that if they only tried a certain diet—and stuck with it—they would surely lose weight. Yet these individuals had already tried such diets—and they had not worked. Doctors, it seemed, could do better.

My desire to speak more sensitively and empathetically to my patients about weight recently led me to read Jonathan Engel’s Fat Nation, a new book that puts obesity in its proper historical and cultural context. Engel’s book can help me—and other health providers—learn how to say the right things to our overweight patients.

Engel, a professor at Baruch College of the City University of New York and the author of several other books on medicine and health policy, cogently argues that over the past 75 years, a “toxic confluence of lifestyle changes, eating habits, available foodstuffs, and social mores” has created America’s obesity epidemic. The statistics he quotes are familiar: Over two-thirds of Americans are either overweight (body mass index of 25 to 30) or obese (BMI over 30), making the United States the “fattest industrialized country in the world.” But the way he frames this confluence of factors is refreshing; his expansive view of the problem discourages blaming individuals in favor of acknowledging and trying to alter the complex sociocultural factors that have promoted weight gain.

For those needing a quick primer on our current physiological understanding of obesity, Fat Nation does a great job. Over the past few decades, scientists have learned an enormous amount about how leptin, insulin, and other hormones control weight. (Several successful surgical procedures to promote weight loss have built on this knowledge.) More recent work has documented how damage to the human biome—bacteria that reside in the gut—from things like overuse of antibiotics can promote obesity. We also now know that genetics exert a major influence on weight, belying old theories that obesity resulted primarily from poor willpower. As Engel documents, studies of both twins and adopted children demonstrate that biology is far more likely to determine one’s weight than the environment in which one is raised. Much attention has also recently been paid to “set points,” a “preferred” weight that one’s body strives to achieve—that is, the body’s physiology pushes dieters toward a certain weight, regardless of what they eat.

At first blush, a genetically driven understanding of weight would seem to run counter to the dramatic rise of obesity in the United States and other countries. After all, why would we expect DNA circa 2018 to be that different from DNA circa 1918? As Engel explains, it is not. Rather, our changing social and cultural environment has coupled with a genetic predisposition to obesity that has always been present to create the current epidemic.

How has our environment evolved historically? For one, we are a far more sedentary society. Suburbanization and other demographic changes have eliminated “livable and walkable outdoor space.” Couple this with sedentary jobs in front of computer screens that have replaced work in factories and on farms, and you promote weight gain. This problem extends to childhood, where kids no longer play outside after school but are shuttled from activity to activity by car—all the while staring at their cellular devices or television sets. And sure, it’s true that people can work to be more active in a world that increasingly incentivizes being sedentary. But it’s worth recognizing that each person pushing themselves to do this is perhaps not the best answer

Engel also sees the rise of fast food as a major culprit in the rise of obesity. Not only is such food—which started at the 1904 St. Louis World’s Fair and now is a ubiquitous presence—high in fats and carbohydrates, it is relatively cheap. Plus, fast food establishments have gradually expanded portion sizes to make more money. Much of this food is what is called high-glycemic. It quickly raises blood insulin levels, which leads to rapid absorption of the food by the body. So not only do customers eat too many calories, they also end up hungry soon after eating. There are other structural changes that cause similar problems, as Engel points out.

Those ubiquitous vending machines that one now sees in hospitals, workplaces, schools, and universities? They represent a constant temptation to potential consumers, leading to excessive snacking, even when people are not hungry.

Perhaps the most important takeaway point from Fat Nation is that obesity is different in different people. I suspect that physicians’ lack of understanding of this phenomenon helps to explain some of the angry responses to my article. Yes, it’s true that a plant-based Mediterranean diet is an effective weight loss strategy for some people, as is Weight Watchers, with its emphasis on behavior modification. But these successful programs simply do not work for many people.

Engel’s most interesting chapter may be the one entitled “Self-Control.” Despite growing evidence that willpower is not a useful concept for getting people to lose weight, the perception persists that the obese just need to try harder. But we now know that different people have different degrees of self-control, and this seems to be hard-wired. It’s not that some obese people won’t stop eating; it’s that they can’t. And while many people eat only when they are hungry, others always feel the need to eat, regardless of how full they are. This is extraordinarily useful information that can help inform how we health professionals best advise our patients.

In the comments in response to my article, it was clear that the condescension and disdain that these writers had apparently experienced from doctors had been devastating to them. This evident pain initially led me to wonder whether we physicians should just start tiptoeing around the subject of obesity, lest we offend.

But this is exactly the opposite of what our patients need from us. Far from avoiding discussions of their weight, they need us to understand more about the issue.  Engel’s book, and the new literature he cites, can help providers learn the best available science and thus have the greatest chance of helping their patients. (It is important to mention that some obese patients may not desire any advice, and doctors should listen to that request. Indeed, some experience few negative health effects from extra weight.)

So what does the new science say that health professionals—with or without the help of nutritionists—should advise? The main way to help obese people lose weight is to help them change their environments. Currently, people must exert exceptional energy resisting the ubiquitous food—often junk food—that permeates their lives. “Resisting tempting food is hard for most people,” Engel writes, “and doing it constantly is exhausting.” It’s possible for individuals to retool their work and home lives to minimize access to unhealthy foods.

But it would be far better if we could figure out more systematic ways to change everyone’s environment for the better—particularly because this would benefit lower-income people who might not have the ability to exert as much control over their environments. Engel thus ends Fat Nation with the suggestion that we ought to address obesity as a societal problem susceptible to laws and regulations, much as we successfully did with cigarettes. Engel notes that the food and restaurant industries will oppose initiatives such as junk food taxes, bans on supersized drinks and jumbo candy packages, mandatory standardized portions in restaurants, and the elimination of candy and cookies from school vending machines, but these efforts will help overweight people without constantly bugging them to change their behavior.

So yes, I will continue to raise the topic of weight loss with my overweight and obese patients. I will also keep listening and trying to learn more—along with avidly supporting more global strategies for helping my patients.

Originally published on Slate.com on December 18, 2018.