America's ever-expanding waistline makes front-page news on a regular basis, as health professionals and policymakers labor to stem a growing tide of cardiovascular disease, hypertension and type-2 diabetes. But now, drinking alcohol may be ruled out as a cause for weight gain, at least for women.
Women of a normal weight who consume alcohol in moderation appear to gain less weight over time than nondrinkers, according to a study published in the March 8 issue of Archives of Internal Medicine. The results of the study point to intriguing potential avenues for research regarding the metabolism of alcohol.
Drinking alcohol would seem to be a plausible culprit for weight gain. Nutritionists point out that people tend to underestimate the calories in the beverages they drink. Each gram of alcohol has 7.1 calories—higher than equivalent amounts of carbohydrates or proteins, which contain 4 calories per gram (by comparison, a gram of fat contains 9 calories). Consuming more alcohol—and thereby more calories—would logically lead to more pounds.
But that wasn't what a research team at Brigham and Women's Hospital in Boston, headed by Dr. Lu Wang, found when examining almost 13 years of data collected from 19,220 female health-care professionals. They selected women over the age of 39 without preexisting medical conditions who had a normal weight for their height (18.5 to 25 on the Body Mass Index scale) and tracked their lifestyle choices via a questionnaire administered every four to nine years.
Nearly all the women gained weight as they got older. But those who didn't drink alcohol gained on average 8 pounds, while the women who reported drinking alcohol gained less, with those who drank 30 to 40 grams of alcohol a day (the equivalent of around three to four 4-ounce glasses of wine) gaining the least, at an average of 3.3 pounds. "Our study results suggest that women who have normal body weight and consume a light to moderate amount of alcohol could maintain their drinking habits without gaining excessive weight," wrote the authors.
Moreover, women who drank alcohol were less likely to become obese or overweight. Roughly 41 percent of the women became overweight (a BMI over 25) or obese (BMI over 30) during the tenure of the study, and the abstemious were the most likely to be included in those categories. Women who drank 15 to 30 grams of alcohol a day (the equivalent of two to three glasses of wine) were the least likely to pass that threshold, with a lower risk of about 30 percent.
This effect carried across all categories of alcohol: red and white wine, beer and spirits, with consumption of red wine showing the strongest link with lower weight gain, and white wine showing the weakest, but still a significant association.
The results cannot be explained away through lifestyle choices, though there were marked traits among women who reported regular consumption of alcohol. They were, on average, more likely to be older, white, smokers and post-menopausal. While moderate drinkers showed the highest level of physical activity, drinking alcohol was associated with a diet of nutritional no-nos: Drinkers were more likely to eat red meat and high-fat dairy products, but not fiber or whole grains. Even after researchers statistically accounted for lifestyle and genetic factors, however, the inverse association between drinking alcohol and weight gain remained significant.
Interestingly, women who drank alcohol appeared to ingest more calories overall than nondrinkers, but fewer calories in their diet came from sources that weren't alcohol. The study's authors raise the possibility of differences in the way our bodies process alcohol in comparison to other caloric sources. For instance, previous studies have shown that heavier women metabolize alcohol more efficiently than leaner women.
Metabolic differences could explain why this effect is not seen in studies of men who drink alcohol. In fact, some studies show that men who drink alcohol gain weight at a greater rate in comparison to their abstemious counterparts. Men have a greater proportion of alcohol dehydrogenase, the enzyme that helps process alcohol in the body, and this difference could explain why men who drink might gain weight faster.
The study's authors also point to research that has shown that after consuming alcohol, men exhibit a moderate change in energy expenditure, while women show a substantial increase, meaning that women could potentially show a net loss of calories after consuming alcohol beverages.
Potential applications for further research aside, the study's authors stress the limitations of their methodology. Self-reported data on weight and alcohol consumption means that the validity of the study hinges on how accurately their subjects could remember and relay their choices. Plus, the study did not differentiate between women who drank a glass of wine every day with those who drank seven drinks on one day of the week, meaning that behavioral factors could further muddy the results.
And the authors cautioned against interpreting the results as a recommendation to drink for the prevention of obesity, noting the numerous problems—both medical and social—associated with drinking. For now, they call for further research into the role of alcohol in weight management. Bonnie Taub-Dix, a nutritional consultant and spokesperson for the American Dietetic Association, agreed. "A study like this could be interesting," she said. "But don't treat this as an invitation to run to a liquor store."