In a 13-year study, Dr Lu Wang and colleagues at the Brigham and Women's Hospital, Boston, found that women who drank more alcohol were less likely to become overweight or obese.
Researchers used questionnaires to record the alcohol and weight of 19,220 US women. The participants were aged 39 years or older, had a BMI of 18.5 to 25 and were free of CVD, cancer and diabetes.
After 13 years, 41.3 per cent of women had become overweight or obese. The researchers found there was an inverse association between alcohol consumption and weight gained across age groups.
How significant are the results?
Previous studies into the effect of alcohol on women's weight have produced mixed results, with inverse and null trends recorded.
This study, published in Archives of Internal Medicine, is the first to examine a link between alcohol intake and obesity risk, the authors said.
The inverse relationship between alcohol consumption and weight gain found in this study became even stronger once the results were adjusted for lifestyle characteristics.
These include baseline weight, smoking habits and physical activity levels. This effect was most pronounced among younger women.
However, benefits did not increase further for those drinking more than around four units of alcohol per day.
Red wine had the strongest association, though researchers found a reduced risk of obesity in drinking beer, white wine and spirits as well.
To explain their results, the authors turned to differences in alcohol consumption habits between men and women.
Studies have shown women are more likely to substitute alcohol for foods without increasing total energy intake, the researchers said.
They added that female drinkers appear to have reduced alcohol dehydrogenase activity and so their bodies use other, more energy-demanding, processes than men to degrade alcohol.
Furthermore, alcohol drinking habits may change appetite and perception of satiety, the authors said.
Should advice change?
The authors said that while normal-weight women who consume alcohol may maintain drinking habits without gaining excessive weight, advice must bear in mind the potential complications of high alcohol consumption.
'Further investigations are warranted to elucidate the role of alcohol intake and alcohol metabolism in energy balance and to identify behavioural, physiological and genetic factors that may modify the alcohol effects,' the authors concluded.
Don Shenker, chief executive of Alcohol Concern, said the health benefit from moderate alcohol consumption was a complex subject and advised caution.
'Alcohol consumption in any form carries risks, although drinking in moderation carries the least risk,' said Mr Shenker.
'To suggest that drinking in moderation is preferable to not drinking ignores the risks of cancer, liver disease and heart disease that can occur when drinking even small amounts.'