Women around the world were shouting “Cheers!” to Tuesday’s news reports about a study that found that women who drink moderate amounts of alcohol (a drink or two daily, particularly red wine) gain less weight at midlife than women who don’t drink at all.

The headlines were, well, drunk with the good news: “Bottoms Up for Skinnier Bottoms” (Independent—Great Britian), “A Drink a Day Could Help Keep the Pounds Away” (Globe & Mail — Canada), “Cheers! Wine Refines the Waist” (Herald Sun — Australia), “Wine Isn’t Fattening, Ladies!” (Hindustan Times — India), and “Want to Stay Thin? Have a Drink” (Women’s Day — U.S.).

Wow! Who needs to hop on the elliptical machine daily, or count calories, or forgo Toblerone chocolate bars? As one of these news accounts put it, just “sipping a glass of Pinot Noir each evening will help keep you in shape.”

What’s not to like about that diet plan?

Before you restock your wine cellar, however, you’ll want to read behind those headlines.

Yes, the study, which was published in this week’s issue of the Archives of Internal Medicine, did find an association between light-to-moderate alcohol consumption and a lower risk of becoming overweight or obese at midlife. But the study (a prospective cohort one) wasn’t designed to determine cause-and-effect.

In other words, the study can’t say that the alcohol directly contributed to the drinking women not gaining as much weight as their nondrinking peers. Other factors that the researchers didn’t adjust for in their analysis could have been involved in the drinkers’ slower weight gain.

Furthermore, the average difference in weight gain between the women who drank moderately and those who abstained was slight — about 5 pounds.

The study’s details
Here, briefly, is how the study was conducted: Researchers at Brigham and Women’s Hospital in Boston gave 19,220 normal-weight participants (aged 39 and older) in the large, long-term Women’s Health Initiative a questionnaire about their drinking habits. They then followed the women’s weight for up to 13 years.

Not too surprisingly, the study found that, on average, all the women gained some weight. Indeed, 41 percent of the women became either overweight or obese (based on BMI calculations) during the course of the study. But, the study found that those who tended to gain the most weight were the women who abstained from alcohol — even after adjusting the data for such factors as smoking, physical activity levels, postmenopausal hormone use, and history of diabetes and high blood pressure.

The abstainers gained an average of about 8 pounds compared to about 3 pounds for their moderate-drinking peers.

The reason for this difference is unclear, but the study’s authors suggest that women drinkers may substitute alcohol for other foods in ways that doesn’t increase their total intake of calories. Or perhaps the alcohol is changing the women’s metabolism in a way that keeps some excess pounds off.

The study’s limitations
All studies come with caveats, and this study is no exception. As its authors note, the study’s participants self-reported both their weights and the amount of alcohol they consume. Such self-reports can be unreliable.

The study also couldn’t determine the women’s specific drinking patterns. Did they consume all their weekly alcohol in one sitting or did they spread it out throughout the week?Differences in drinking patterns might make a difference in weight gain.

And, again, something else in the daily habits of women who drink moderately — something not picked up by this study — may have been responsible for their slower weight gain.

Given the study’s limitations and the known health risks from regular alcohol consumption — especially, an increased risk of breast cancer — no woman should use these findings to change her drinking habits.

As James C. Garbutt, a professor of psychiatry at the University of North Carolina’s Bowles Center for Alcohol Studies, told the Los Angeles Times: “If the message is that by drinking some alcohol you’re going to lose weight, that’s a potentially complicated and dangerous message.”

No matter what some of the news headlines say.