Researchers at Brigham and Womens Hospital in Boston asked more than 19,000, normal-weight US women aged 39 or older how many alcoholic beverages they typically drank in a day, and then tracked the women for around 13 years.

The largest single group -- 7,346 women or just over 38 percent -- said they didn't drink a drop, according to the study published in the Archives of Internal Medicine, a publication of the American Medical Association.

The second biggest group -- 6,312 women or nearly a third of those surveyed -- reported drinking the equivalent of around a third of a five-ounce glass of wine or a third of a 12-ounce beer. They did not explain how they managed to do so.

Twenty percent of the women said they drank the equivalent of up to a glass of wine, a 12-ounce beer, or a single-shot drink made with 80-proof spirits, while six percent said they had up to two drinks a day and three percent had more than two.

Over the 13-year follow-up period, the women who did not drink at all gained the most weight, and the women who had the equivalent of two drinks a day were the least likely to pack on pounds.

The best drink for keeping the pounds off was red wine, but all four types of tipple included in the study -- red or white wine, beer and spirits -- showed the same "inverse association between alcohol intake and risk of becoming overweight or obese," the study found.

Read more at A tipple a day keeps obesity at bay.