Sunday, May 20, 2012

When in doubt, blame the journalist: prenatal dieting edition

Sometimes bad science reporting makes me laugh, and sometimes it actually kind of stresses me out.  This is one of the "this stresses me out" times.

The headline reads: Diet during pregnancy is safe and reduces risk for complications, study finds

Now aside from being a bit on the garbled side, it's a pretty provocative headline.  As someone who has been in and out of obstetrician's offices for the past 7 months or so, it also runs counter to everything I've been told.  According to this write-up however, here's a few things this study found:

 Is it safe for a pregnant woman to go on a diet? According to a new study, not only is it safe, but it can even be beneficial and reduce the risk of dangerous complications.
That would seem to contradict what my doctor has told me....but let's read on (to what they found about dieting methods):
The researchers found that all three methods reduced a mother's weight, but diet showed the greatest effect with an average reduction of almost 9 pounds. Pregnant moms who only exercised lost about 1.5 pounds, and moms who did a combination of diet and exercise lost an average of 2.2 pounds.
So they had mothers to be lose weight during pregnancy?  That seems....extra wrong....but go on:
Women who went on a calorie-restricted diet were 33 percent less likely to develop pre-eclampsia, a spike in blood pressure caused by significant amounts of protein in the urine.
Wait, now I know he's just phoning it in.  Pre-eclampsia is not high blood pressure caused by protein in the urine, it's high blood pressure AND high protein in the fact the Mayo Clinic article he links to says so.  

At this point, I took a look at the original study, and found other "oops" moments in the reporting.  First, the study never looked at "diets".  What they actually looked at was "dietary interventions"...which they describe as follows:
Typical dietary interventions included a balanced diet consisting of carbohydrates, proteins, and fat and maintenance of a food diary. 
Since this was a meta-analysis, I took a look at the references, and in fact only one study cited directly looked at caloric restriction....the sort of thing most of us think of when we hear the word "diet".

Furthermore, that part about the women's weight being reduced?  It wasn't.  Their weight gain was reduced.   ...something the study authors are clear about, but the subsequent write up completely leaves out.

I actually got a little angry about this.  You can feel free to blame pregnancy hormones, but I find this sort of thing is just irresponsible.  CBS is a major news network, and people are going to take what they say seriously.  As the Assistant Village Idiot likes to point out, people believing faulty science on small things can be funny and doesn't matter much....but when you realize bad studies could actually affect the way people live, it gets scary.  Someone following this story could do some real damage.  In fact, the article does get clearer towards the end (when it quotes the original study author), but that's 6 paragraphs in.  It drives me nuts that a good a carefully thought through study can get reported so sloppily and potentially dangerously.  There is a world of difference between what most of us think of when we say "diet" and what the researchers here described, which was essentially just formalized pre-natal nutritional counseling.

Overall, real dieting during pregnancy is still dangerous....and can backfire in a big way.  Mother's who are forced to restrict calories during pregnancy (famine victims, etc) actually wind up having children who are more likely to be obese and develop diabetes.  As a side note, one of the most fascinating studies on this is the Dutch Famine Study where mother's who had temporary famine conditions during pregnancy could be studied for the long term effects on the children.

This is why it matters that the media report things correctly.  People should not walk away from reading about good science with bad ideas.  Words like "diet" or "weight reduction" do not mean the same thing as "dietary interventions" or "weight gain reduction". No one should have to read to paragraph 7 to get accurate information.  That's just bad form.

The only thing that could have made this story worse would have been an infographic.  I'm going to have nightmares about that tonight.


  1. I wish this sort of culpable incompetence was isolated. Journalism schools must teach their students how to write, but not how to read. They know the party line, but not much else.

    I'm told the Daily Mail (Drudge links to them from time to time) has borrowed a leaf from the NYTimes and now and then just makes something up.

    1. The worst part about reading this article is I actually think he was trying not to plagiarize other sources so he just mixed around sentences at random.

  2. Jonathan was high birthweight at 8-3, largely because of Tracy's full nutrition and hence, weight gain. When he had failure to thrive and went down to 5-5 at two weeks, he had zero to spare. He very nearly died, hospitalised for a week. Not a hard sell to Tracy to not worry about weight next time around (Ben came in at 9-5).

    Yet the generation before ours women were routinely kept from gaining too much weight - some doctors would say 14 lbs, some 18 - and were even put in hospital so that doctors could control their eating.

    1. Isn't that the same generation that was told Thalidomide was a good idea and that deliveries with forceps were just fine?

      Didn't know that about Jonathan. Scary stuff.

  3. This is really fascinating, You are a very professional blogger. I’ve joined your rss feed and sit up for searching for more of your great post. Also, I have shared your site in my social networks! black hat python