“Slow-chewing” study news release begs a mouthful of questions

A news release about a study from the University of California San Diego (UCSD) Jacobs School of Engineering claimed recently that “Chewing slowly helps prevent excessive weight gain in children.”

That release was subsequently reposted and picked up by a number of news stories across the web that passed along the claims uncritically. Some examples:

Yahoo News: Chewing slowly helps prevent excessive weight gain in children

Healthnewsline: Slow Chewing Can Help Prevent Childhood Obesity – Study

Tech Times: Slow Chewing Of Food May Help Prevent Kids From Gaining Excess Weight

The basic claim here is that asking children to chew each bite of food for 30 seconds helps them lose weight compared with chewing normally.

While that might sound reasonable on its face, reading this study for more than 30 seconds would have generated a number of questions about the research that should have been addressed in the coverage. As obesity expert and HealthNewsReview.org contributor Yoni Freedhoff, MD, pointed out to me, the “slow-chewing” group received all sorts of instruction and advice, besides the 30-second guideline, that could have helped them maintain a healthier weight compared with the control group, which received no instruction at all.

The study itself notes that “Participants and parents were shown the appropriate weight by age, main causes of obesity or dyslipidemia in children and adolescents, complications of obesity such as diabetes, and which foods are recommended and not recommended for healthy growth.”

In addition, the slow-chewing group (but not the control group) was instructed to also:

1. Eat home cooked meals
2. Eat at a table
3. Use an hourglass to guide eating speed
4. Drink water before starting to eat
5. Possibly avoid sugary drinks
6. Do not eat and talk at the same time
7. No repeated portions
8. No overfilling
9. No eating or snacking between meals
10. No eating off the table

The researchers also supposedly compared results between those in the “slow-chewing group” who adhered to the slow-chewing advice and those who didn’t — finding that the slow-chewing adherents lost weight while the non-adherents gained weight.

But there are some problems with that analysis: 1. the researchers only asked whether participants used an hourglass timer at meals, not whether they actually chewed slowly 2. The group of slow-chewing “adherents” included just 14 children, and 3. How do we know that these adherent children weren’t also more adherent to all the other behaviors that the researchers prescribed and which could be much more important for preventing weight gain?

Had any of these stories bothered to ask an independent expert about these findings, they might have heard and passed along to readers something similar to what Freedhoff told me.

“You don’t need to have a background in statistics to know that if an intervention includes 11 separate behaviors, measuring only one would not allow for any conclusions to be drawn. That reporters didn’t question the findings to me suggests they didn’t even bother to read the paper. Putting that concern aside, uncritically reporting that chewing each bite of food for 30 seconds may be a viable lifelong strategy for weight control suggests to me that they also didn’t bother to think about the news release – and if you’re wondering why, I invite you, at your next meal, to chew each bite for 30 seconds to find out.”

A bright spot here is that all the major health news outlets (e.g. national dailies and wire services) appear to have stayed away from this story and its selective emphasis on slow-chewing. Why give life to a story that isn’t really a story?

UCSD, however, should have known better than to promote this preliminary study without qualification. After all, the researchers themselves acknowledged the difficulty in teasing out what exactly accounts for the benefits seen in the slow-chewing group. “The enduring changes in diet and the compliance in the current study were most likely attributable to recurring contacts with the same study personnel and immediate feedback to the subjects,” they wrote in the study. “Therefore we cannot exclude a significant contribution due to simple advice in the form of constructive talks and encouraging messages inherent to the implementation of our program nor an effect related to self-monitoring.”