Friday, April 17, 2009

if it sounds too good to be true-it is

Could it be that easy? Just cut out the soda and the "childhood obesity epidemic" would be a thing of the past?

Recent headlines:
"High calorie drinks cause childhood obesity."
"Cut the soda, cut the fat."

The study did not have highest scientific standards. Kids estimated their intake (not the most reliable way to measure actual intake) for two days, and then the study "estimated" the effects of replacing soda intake with water. There was no actual intervention arm that had two groups, one drinking soda, one drinking water to measure results. (I'm not saying drinking less soda is a bad idea, I'm just skeptical of claims that doing so would result in dramatic weight loss, or any weight loss.) The authors call this a "key strategy" and simple and effective way to prevent childhood obesity. 

the science

In fact, the American Heart Association reviewed 50 years of data: "Studies in diet composition in children do not identify causes of obesity in youth." In other words, they were unable to find any cause- not soda, juice, fat etc. 

The DONALD study had thousands of kids followed over 17 years (much larger, more accurate, complete study than the headline grabbing soda-diet study) showed the same thing. This study looked at sugars, processed foods, fiber, in fact every imaginable combination of foods and was unable to even link (in spite of their best statistical efforts) diet composition and body mass index or weight. In other words, kids ate a huge range of calories and nutrients but you could not predict the size of the child based on the diet.

Study that actually did limit soda in schools

Another study actually looked at the effects of limiting soda in schools and found no difference in weight at the end of the study.  (Where was the national press attention here?)

(Fernandes, Meenakshi, The Effect of Soft  Drink Availability in Elementary Schools on Consumptiion. Journal of the ADA. 2008 1445-1451 Studied 10, 215 5th graders.

Here are a few quotes:

“soft drink availablitity at  school may have limited impact on overall consumption for elementary school children.” 

 “Overweight children were not more likely to purchase soft drinks.”  

“The removal of soft drinks from schools is estimated to decrease the share of children who consume soft drinks by 4%, but without significant impact on overall soft drink consumption.” 

And yet the author concludes sodas need to be removed, school areas should rezone so kids can’t go to fast food to buy soda etc…

What it means: Unhealthy weight gain is a complex issue. Genes, stress hormones, chaos in the home, parental feeding styles, cycles of restriction and bingeing, lack of structure and grazing, dieting,  and anxiety about weight all play a role. No single or even combination of dietary factors predicts weight, so interventions based solely on diet fail. While we may desperately seek a quick and easy solution, so far there hasn't been one. I again would argue that HOW we feed kids is the missing piece. 


  1. Like the entertainment industry, the media chooses to print studies that will get readers attention regardless of their credibility or lack thereof. Yesterday, a study which concluded that overweight people create more greenhouse gases was getting international attention; maybe because today is Earth Day and the media services knew it would be controversial? We almost have to be scientists ourselves to evaluate these studies, look at their parameters, control groups, etc. to determine if they have any merit.

  2. I agree. I took many classes in medical school and residency to learn how to evaluate the merits of a study and its still hard. It takes time and effort to look at the real numbers ( does a really good job at this and has explanations about stats, terms used etc.) Even the science reporters are lazy and tend to just write stories off press releases. Alas we're all so busy we just pay attention to the headlines which have to be scary or otherwise standout-like your example-to get our attention... Sad state of affairs.