Thoughtful consumers with even a modest knowledge of health and medicine can discern at a glance that they are bombarded by superficial and sometimes misleading “news” of fad diets, miracle supplements, vaccine scares, and other exotic claims that are short on science, as well as endlessly recycled everyday advice, such as being sure to slather on sun protection. But often, even articles written by very good journalists, based on thorough reporting and highly credible sources, take stances that directly contradict those of other credible-seeming articles.

There is more at stake in these dueling stories than there would be if the topic at hand were, say, the true authorship of Shakespeare’s plays. Personal healthcare decisions affect our lifespan, the quality of our lives, and our productivity, and the result—our collective health—has an enormous impact on the economy. Thirty years ago, misleading health information in the press might not have been such a problem, since at the time physicians generally retained fairly tight control of patient testing and treatment decisions. Today, however, the patient is in the driver’s seat when it comes to personal health. What’s more, it is increasingly clear that the diseases that today wreak the most havoc—heart disease, cancer, diabetes, and Alzheimer’s—are most effectively dealt with not through medical treatment, but through personal lifestyle choices, such as diet, exercise, and smoking habits.

Consider the potential damage of bad weight-loss-related journalism. Obesity exacerbates virtually all major disease risks—and more than one in 20 deaths in the US is a premature death related to obesity, according to a 2007 Journal of the American Medical Association study. Obesity carries an annual price tag of as much as $5,000 a year in extra medical costs and lost productivity, for a total cost to the US economy of about $320 billion per year—a number that could quadruple within 10 years as obesity rates climb, according to some studies. (There is, of course, a lot of uncertainty in cost projections, and this research does not account for the impact of the Affordable Care Act.) On top of these costs are the subjective costs of the aches, discomforts, and compromised mobility associated with obesity.

Meanwhile, there’s a wide range of convincing-sounding yet wildly conflicting weight-loss-related claims made by prominent science journalists. People who might otherwise be able to lose weight on the sort of sensible, lifestyle-modification program recommended by most experts end up falling for the faddish, ineffective approaches touted in these articles, or are discouraged from trying at all. For example, innumerable articles (including Parker-Pope’s Times piece) have emphasized the notion that obesity is largely genetically determined. But study after study has shown that obesity tends to correlate to environment, not personal genome, as per the fact that people who emigrate from countries with traditionally low obesity rates, such as China, tend to hew to the obesity rates of their adopted countries. What’s more, global obesity rates are rapidly rising year by year, including in China, whereas the human genome barely changes over thousands of years. And studies clearly show that “obesity genes” are essentially neutralized by healthy behaviors such as exercise.

It is not encouraging to those trying to muster the focus and motivation to stick to a healthy-eating-and-exercise program to hear that their obesity is largely genetically determined, suggesting—sometimes explicitly—that the obese are doomed to remain so no matter what they do. A 2011 New England Journal of Medicine study (as reported in The New York Times) found that people tend to binge after they find out they carry a supposed fat-promoting gene. Other studies have shown—in keeping with common sense—that one of the best predictors of whether someone starting a weight-loss program will stick with it is how strongly the person believes it will succeed. When journalists erode that confidence with misleading messages, the results are easy to predict.

When science journalism goes astray, the usual suspect is a failure to report accurately and thoroughly on research published in peer-reviewed journals. In other words, science journalists are supposed to stick to what well-credentialed scientists are actually saying in or about their published findings—the journalists merely need to find a way to express this information in terms that are understandable and interesting to readers and viewers.

But some of the most damagingly misleading articles don’t stem from the reporter’s failure to do this. Rather, science reporters—along with most everyone else—tend to confuse the findings of published science research with the closest thing we have to the truth. But as is widely acknowledged among scientists themselves, and especially within medical science, the findings of published studies are beset by a number of problems that tend to make them untrustworthy, or at least render them exaggerated or oversimplified.

David H. Freedman is a contributing editor at The Atlantic, and a consulting editor at Johns Hopkins Medicine International and at the McGill University Desautels Faculty of Management.