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Recent discussion about “obesegons” – chemical triggers for obesity that have nothing to do with lifestyle or diet or genetics – at the annual meeting of the American Association for the Advancement of Science has captured the imagination of science reporters (see here, and here). And the theory that even very low exposures to environmental chemicals may play a role in obesity was given a further push into public consciousness by news accounts of a new study linking phthalates to obesity in men.

“Fat Man in the bathtub? Blame chemicals,” said the headline in the Seattle Post Intelligencer, which advised readers to,

“Check out this study on phthalates from Environmental Health Perspectives that says phthalates, which are increasingly implicated in health problems, contribute both to abdominal obesity and insulin resistance in men. This would need to be confirmed by further and larger studies for it to be significant, but it gets ya thinkin'.”

It sure does, but more for the fact that, if you follow the link, the study doesn’t actually say that phthalates “contribute both to abdominal obesity and insulin resistance in men.” Rather, the study found that “several phthalate metabolites showed statistically significant positive correlations with abdominal obesity and insulin resistance in adult U.S. males,” which is something quite different. Namely, the fatter and more insulin resistant the man, the greater the quantity of phthalate metabolites in his urine.

But the simple fact of a correlation doesn’t mean that phthalates caused the obesity; it could be the case that men who are fat retain more phthalates than men who are not. In fact, the authors of the study listed seven limitations on the interpretation of their findings, among which include the study being cross-sectional, so it is only a snapshot of at a single point in time and cannot determine causality; and the database they used contained no data on sex hormone levels, thereby limiting examination of the mode of action by which they hypothesize that phthalates might cause obesity.

While this research is very interesting from a scientific perspective, it is also very vague, which is problematic from a public health perspective, when news organizations convey this vagueness to the public in far less circumspect “Fat? Blame Chemicals” headlines.

“A new study shows a class of chemicals found in plastics sometimes found in toys and soaps could be what's causing obesity in men,” said ABC7 in Chicago.

“Exposure to a class of chemicals commonly found in soap and plastics could be fueling the obesity epidemic by contributing to abdominal obesity and insulin resistance in men, a new study suggests,” said Yahoo news.

The risk is that people take away the message that obesity is something that is somebody else’s fault, beyond their control, and that they can forget about such proven factors behind obesity, such as poor diet and a lack of exercise.

At the same time that America was starting to obsess about hypothetically “fattening” chemicals, Britain, which has similar obesity rates to the U.S., was looking at a bigger and less “suggestive” problem. A report by Britain’s Medical Research Council (MRC) found that parents were a major factor in rising rates of childhood obesity.

As the Guardian reported, the MRC found:

“· Parents often have no idea that their child is overweight and know little about the damage that could do to their health.

· Parents sometimes think changing to a healthy lifestyle would be too difficult.

· Parents are under pressure to provide high fat, salt and sugar food, not just from advertising, but from their children who do not want to be different from friends.

· Parents think it is not easy for their children to have an active lifestyle because sporting activities can be expensive and playing out may be dangerous.

The report finds evidence that parents are not in control of their children's eating habits, because they do not want to fight over food, or because they assume it is good for children to make choices. Some 40% of children aged six to nine choose their evening meal as a result.”

How much do you want to bet that these children are choosing to eat fresh vegetables and lean meats and fish?

So here we have a study in contrasts: news that focuses on medical findings documenting some very disturbing dietary findings versus news that focuses on a hypothesis with extremely limited data. Now which set of data do you think advances public health?