Tuesday, March 09, 2010


That's supposed to be something you say when having a toast. Like "bottoms up!" A new study finds that moderate drinking in women is correlated with gaining less weight in middle years:

In the study, researchers at Brigham and Women's Hospital in Boston examined data from 19,220 women enrolled in the long-running Women's Health Study. The women, all ages 39 and older at the start of the study and all originally of normal weight, provided information on questionnaires about their alcohol intake as well as other health and lifestyle information over an average of 13 years.

To assess the impact of alcohol only, researchers adjusted for other factors that are known to influence weight, such as smoking, body mass index, age, non-alcohol dietary intake and physical activity. They found that compared with women who abstained from alcohol entirely, women who drank between 15 and 30 grams a day _ the equivalent of a drink or two _ were 30 percent less likely to be overweight or obese at the end of the study period.

Note that word "correlated" in my first paragraph. It's not the same as saying that drinking moderately caused less weight gain, all other things being constant. That is, indeed, one intriguing possibility. But as the authors of the study note, there are other possibilities.

One I immediately thought about is that "moderate drinking", especially the consumption of red wine (which was the type of drinking most correlated with less weight gain), might have shown a social class or income difference over the last few decades. If that is the case, this variable could pick up not only the person's drinking habits but perhaps also aspects of lifestyle which vary by income.

For instance, it could be that the same dietary intake of two women with different incomes might not in fact be the same in the quality of food consumed and in its ability to cause weight gain. The wealthier might eat fresher food, with fewer additives, say.

Or perhaps not. It could be that moderate drinking does increase the metabolic rate in women. But it's always useful to remember that different variables in empirical studies (such as drinking in this one) may carry lots of unintended baggage and in fact measure more than one underlying theoretical variable.