I love reading research articles. I've been shuffling through them since they were required reading in college. I like to devour the articles looking for trickery in language and leaps of faith in logic phrased in fancy-schmancy scientific double-speak used to make it sound like the researchers discovered something that may not be true.
In my mind I see a room full of scientists typing away, going through multiple edits and revisions. They are desperate to get their work published and fulfill years of planning and research and experimentation. They are living a lifetime of all my grad-school all-nighters. These writers of my imagination are trying to secure a legacy, get published in a major medical journal, or *score* have their title mentioned during Good Morning America.
If you are a scientific researcher and I've just offended you by vilifying your job, I do apologize. Sadly for both of us, my critical thinking skills are at their sharpest when trying to find "the catch". This is especially fun with stories that make it onto Good Morning America or any other morning news brief.
Lucky for you I still don't own a TV, so I haven't seen GMA in months. But our time will come again.
This morning I was handed an article torn from the newest issue of JAMA (Journal of the American Medical Association). It hasn't made GMA yet (that I can tell) but it is getting some press time.
The purpose of the article was to determine a correlation between minutes of exercise and weight gain over time. The observational research was initiated on the premise that the federal guidelines for 150 minutes per week of "moderate intensity" aerobic activity are necessary to receive substantial health benefits are completely arbitrary; not to actually determine any sort of concrete detail on how much exercise we actually need.
First thing to consider when evaluating a study: Who are the researchers talking about? In this study, the subjects were 34,000 middle aged women who were healthy at the end of a previous study (the Women's Health Study). These women did not have heart disease, cancer or diabetes at the start of the study. Their mean age was 54. Think about this. In a country where 1 in 3 people is obese, these researchers have hit a gold mine of extraordinarily healthy middle aged women. Where did they find these people?!
The researchers were able to distribute the women into 3 activity levels and keep a couple of things pretty even. Across all 3 groups the ages are roughly the same, so is the percentage of subjects who are white, as well as the total calorie intake per day (as verified by a food frequency questionnaire). There's an important point here: the women who exercised more ate less fat in those calories and more fruits and veggies than the women in the other groups. Additionally, the women who exercised more had a higher level of formal education and were more likely to use HRT if they were postmenopausal. I'm not sure what HRT has to do with any of this, but it does make me wonder if that means they have health insurance, or at least the means to pay for the drugs.
Another thing to remember in any kind of observational research: attrition. The researchers followed these women for 156 months. At various points in time they are missing data from several hundred women. They can show statistical significance between less weight gain and lower BMI, no history of smoking and increased amount of exercise, but DUH. What were all those people doing who weren't turning in their exercise surveys to the researchers? Were they exercising? Following the curve? Losing or gaining in such a way as to become an anomaly? We'll never know. Would these numbers be the same if they ONLY counted the women who replied?
One important thing they did note was the older subjects who exercised less, gained more weight over time than their younger counterparts. The people who exercised the most and gained the least were younger and started out with a BMI of 25 or less. Does this have to do with metabolism? Menopause? Nah, it's most likely because old habits die hard. The older you are, the harder it is to change your ways. So start young.
So far the news articles I've seen have pulled from this the gleaning example of the study's most successful participants. The people who started out with the lowest weight and gained the least were exercising about one hour per day. (But they were also doing lots of other stuff, see above). News articles will translate this to the recommendation of "exercise one hour per day to prevent weight gain". But remember, this relationship might only apply to you if you're white, college educated, a non smoker who eats a low fat diet that is high in fruits and vegetables and you're continuing these habits into your 50's and you're already leaner than the average American.
Otherwise, all we're looking at is a statistically defined coincidence of events.
And more recreational reading for me.
Article: Lee, I-Min, et al. Physical Activity and Weight Gain Prevention. Journal of the American Medical Association. 2010: 303 (12): 1173-1179
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