nos-trum. pronunciation: \nos'-trum\. noun. Etymology: Latin, neuter of noster our, ours.
1. a medicine of secret composition recommended by its preparer but usually without scientific proof of its effectiveness.
2. a usually questionable remedy or scheme.
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Wednesday, March 24, 2010

The Eternal Triangle: Women, Exercise, and Weight Gain

Women have to exercise til they drop in order to avoid weight gain?

This study in the Journal of the American Medical Association this week (Mar 24/31) is getting a lot of press (WSJ, Mar 24).  My link to the study is for the free abstract only.

What bugs me is the headlines, which say "Women Need 60 Minutes Of Exercise A Day To Not Gain Weight" or some such.  That's not really what the data says.

It does say that "Women successful in maintaining normal weight... averaged approximately 60 minutes a day of moderate-intensity activity."

BUT, and this is a big "but," the only group of women who had a statistically significant association between exercise and less weight gain was that group with a BMI of less than 25.  Recall that BMI is Body Mass Index, which is a calculation of overall body fat based on height and weight.  For instance, if you are 5 feet 6 inches and weigh 160 pounds, you are over the limit (25.9), and not in the group referenced above.  Interested in what your BMI is?  Go here for a quick calculator.

Back to the data to validate this claim.  The study looked at 34K women over the period of 1992-2007.  The study group was a median 54 years old.  All together women gained an average of 2.6 kilos over the course of the study.  The study categorized the women's activity into "less than 7.5 MET hours per week", "7.5 to 21 MET hours per week," and "more than 21 MET hours per week."  A MET (metabolic equivalent) is a measure of exercise:  21.5 MET hours per week  is about 60 minutes of moderate-intensity exercise per day.

Women in the <7.5 category gained 0.12 kilos over 3 yrs.  Women in the 7.5-21 category gained 0.11 kilos over 3 yrs.  Not significantly different.  4540 (13.3%) women with BMI of less than 25 at the start had significantly less weight gain throughout the study.

So, bottom line, the authors conclude that "physical activity was associated with less weight gain only among women whose BMI was lower than 25."  That's a lot different from the headline, because it means if you were skinny before, you're most likely to stay skinny.  Does that sound like an earth-shattering finding?  Conversely if you were heavy before you tend to get heavier.

So, the media is hyping the results...again.  The science is more mundane.

Nothing is changed:  the best prescription is to eat right, exercise, get your rest, and enjoy your life.

Opinions are entirely my own.

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