A lot of people ring in the New Year with vows to lose weight and exercise. In Israel, however, a new law took effect January 1st that banned the use of underweight models. It set a strict limit of a Body Mass Index (BMI) of at least 18.5 (any lower than that, and the World Health Organization considers you underweight and potentially malnourished) for any models appearing on the catwalk or in advertisements. It also required that ads print a disclaimer if they digitally altered the models.

“I helped develop this law in response to the epidemic of eating disorders I was seeing among our young people,” said Rachel Adatto, who led the creation of this law in the Knesset, Israel’s parliament. “So many girls are idolizing these models and wanting to look like them.”

But will eliminating the anorexic ideal actually reduce cases of eating disorders like anorexia, bulimia, binge eating disorder, and others? Here is where eating disorder researchers are less sure.

“This is the subject of lots of speculation. There are people who feel society plays a large role, and there are others who say that it’s genetics and biology that play a big role in the development of eating disorders,” says Walter Kaye, a psychiatrist and director of the eating disorders clinic at the University of California, San Diego.

Much of the media coverage around eating disorders surrounds celebrities and models. Does Barbie cause bad body image in girls? What celebrity has started to talk about his or her eating disorder? Will banning the use of Photoshop in ads keep young people from stopping at nothing to achieve bodies that are completely unrealistic?

The research literature, too, asks these questions, and not without reason. Estimates from the National Health and Nutrition Examination Survey calculate that just under five percent of Americans will experience an eating disorder in his or her lifetime. Rates are thought to be similar in developed countries around the world. And since anorexia nervosa is the most lethal psychiatric disorder and eating disorders are difficult to treat, trying to prevent them from starting seems like a solid approach.

Look more closely at many of these studies, however, and you’ll frequently see the words “disordered eating” in the titles instead of eating disorders. It sounds like a simple adjective switcheroo, but the difference is actually quite a bit deeper than that, says psychotherapist Sarah Ravin.

“Disordered eating really involves two things: an obsession with weight and body image, and a persistent pattern of unhealthy or overly rigid eating behaviors, like constant dieting or eliminating entire food groups. These generally come from the outside, from cultural pressures and messages. Eating disorders, on the other hand, are driven largely by biological processes that occur on the inside. They are eating behaviors that profoundly affect a person’s ability to lead a healthy and productive life,” Ravin said.

Most of the studies used to bolster support for the Israel law and similar measures actually measure links between models, media, and disordered eating, not clinical eating disorders. There are good reasons for this, especially the fact that disordered eating is much more common than eating disorders, which makes it easier to measure outcomes in research studies. As well, many questionnaires and assessments that scientists use to screen for potential eating disorders place these on a continuum with disordered eating. Eating disorders, researchers believed, were essentially more severe forms of disordered eating. Prevent disordered eating, then, and you can prevent eating disorders.

But researcher Cynthia Bulik, a psychologist and professor of eating disorders at the University of North Carolina, Chapel Hill, says that may not be true. She is currently researching the subject using a large cohort of individuals in Scandinavia to determine if eating disorders and disordered eating really are on the same continuum, or if similarities between the two are only superficial.

“We all assume that disordered eating and eating disorders live on a continuum of severity, but we don’t actually know that that is the case,” Bulik said.

Even if disordered eating and eating disorders aren’t the close cousins that scientists previously thought, Bulik points out that disordered eating is still a significant health concern. These individuals are preoccupied with food and weight, and their frequent dieting ironically puts them at risk for excess weight gain. Obsessive exercising and inadequate nutrition can, over time, put people at high risk for overuse injuries like stress fractures. While the potential links between eating disorders and the media remain somewhat hazy, those between media images and disordered eating are much clearer. Exposure to Western media has been shown to increase body dissatisfaction, dieting, and extreme weight loss measures (such as fasting and self-induced vomiting). Disordered eating is also linked to higher rates of depression and anxiety, both in the present and in the future. And while these issues are, by nature, less severe than in clinical eating disorders, they affect a much wider swath of the population.

“Disordered eating is not healthy eating even if it is etiologically unrelated to eating disorders, and if this law has positive effect on reducing disordered eating, that would be a positive public health outcome,” Bulik said.

If the Israel model ban were directed towards disordered eating, Ravin says she would support it whole-heartedly.

“You know, if they said that the goal of this bill was to reduce body dissatisfaction and help promote a wider range of body shapes and sizes in advertising, I would get behind it,” she said.

The problem, she says, is that it’s directed at eating disorders, not disordered eating. Again, the difference can seem subtle and sound more like splitting hairs, but the difference is important. Ravin’s concerns are echoed by Kaye.

“We don’t really have the data to know how much of a role culture plays in eating disorders,” he said. “But the fact is that relatively few women develop a severe eating disorder. If it was just culture, you would expect much higher rates of eating disorders.”

Genetics alone does not an eating disorder make, generally speaking, and Bulik points out that environment still plays a role. While the media is part of this environment, so are other things like being teased about weight, joining a sports team and increasing training, and getting the flu or having oral surgery and being unable to eat properly for several days. Removing one potential environmental trigger for an eating disorder isn’t necessarily bad, but it’s not clear whether another trigger would step in and take its place.

Kaye also points out that eating disorders have long been conceptualized as diets gone too far, and diseases of vain girls who want to be thin at any cost . The work of Kaye and others, however, shows that eating disorders are kept in place because they relieve unpleasant emotions experienced by sufferers. For someone with anorexia, self-starvation makes them feel better. Binge eating and purging does the same for someone with bulimia.

Whether efforts like Israel’s will actually prevent eating disorders remains to be seen. The eating disorder field remains divided over the potential efficacy of such measures. The one benefit that Israel’s underweight model ban has already brought is by getting people talking about the issue.

“This law has really gotten people talking. Parents are talking about it, schools are talking about it, even kids themselves are talking about it. They are becoming more aware of what eating disorders are and what they look like. It’s been a helpful tool to start the discussion we need to have about eating disorders,” Adatto said.