The study was published by Archives of Internal Medicine this week. It is entitled “Alcohol Consumption, Weight Gain, and Risk of Becoming Overweight in Middle-aged and Older Women.” Vol. 170, No. 5, March 8, 2010, p. 453-461.
The study did not set out to investigate women, wine, and weight. Rather, it was a randomized clinical trial evaluating the effects of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer. The findings that have everybody so excited were actually part of the baseline questionnaire. Adjustments were made first for age, then for race, baseline BMI, randomized treatment, nonalcohol energy intake, physical activity level, smoking habits, postmenopausal status, postmenopausal hormone use, multivitamin use, history of hyperchloesterolemia and hypertension, and dietary factors. They did not adjust for income.
One rather interesting find is that, compared with non-drinkers, women who consumed more alcohol were more likely to be white smokers. Women who consumed moderate alcohol also had the highest levels of physical activity.
So what were the results that have everybody so excited? What we are hearing is that “Women of a normal weight who consume alcohol in moderation appear to gain less weight over time than nondrinkers.” Wine Spectator.
Curiously, these results seem gender-specific. The study mentions that its results are consistent with other studies that all had similar findings, specific to women, while alcohol consumption in men lead to weight gain.
Alcohol consumption was divided into different tiers, 0-5 grams per day (g/d), 5-15 g/d, 15-30 g/d, and over 30 g/d. They also noted consumption of more than 40 g/d, but did not include much information at that level in the study.
The key language in the study that has everybody buzzing is:
Compared with nondrinkers, women who consumed more than 0 to less than 5, 5 to less than 15, 15 to less than 30, and 30 g/d or more of alcohol had age-adjusted RRs (relative risks) of 0.96, 0.84, 0.73, and 0.78, respectively, for becoming overweight or obese. The risk of becoming overweight or obese was not further reduced for women consuming 40 g/d or more of alcohol (age-adjusted RR, 0.90 [95% CI, 0.71-1.13]). These RRs changed little after multivariate adjustment. An inverse association between alcohol intake and risk of becoming overweight or obese was noted for all 4 types of alcoholic beverages, with the strongest association found for red wine and a weak yet significant association for white wine after multivariate adjustment.
Let’s break that down a bit. The baseline for the study was the group of nondrinkers. They get a “relative risk” value of 1. “Relative risk” measures the possibility of becoming obese, not as an absolute, but compared to others. A person with a relative risk of 0.5 is half as likely to become obese as a person with an RR of 1. In the study, the RR went down, so the likelihood of become obese went down, as alcohol intake went up. A person who drank 0-5 grams of alcohol per day was 4% less likely to become obese than a non-drinker, while a person who drank 15-30 g/d was only 73% as likely to become obese. Above 30 g/d, the number ticked up slightly, to 78%. (Above 40 g/d the numbers were statistically identical to 30-40 g/d.)
The end of the paragraph notes that the strongest association was for red wine. This is the only sentence in the article that distinguishes one type of alcohol from the other, which is interesting, because the language seems to indicate that only the correlation to red wine has strong statistical significance, white wine a weak but significant association, leaving one to wonder whether there is any statistical significance at all for beer and hard liquor. “Significance,” here, does not mean importance, but statistical significance, meaning a result that is unlikely to have occurred by chance.
This is the latest in a line of studies that showed an inverse relationship between alcohol intake and obesity in women. In studies that looked at both genders the results were different for men. Across the board, in studies from the United States to Norway to China, obesity in men was in a direct relationship, rather than an inverse relationship, to alcohol intake. That was explained by findings that men tend to add alcohol to their daily dietary intake, while women substitute alcohol for other food without increasing their dietary intake. Women also seem to metabolize alcohol differently. Together, that means alcohol intake results in a gain of potential energy intake for men but a loss for women.
So have we found it, the magic elixir, the juice that will keep America’s women lithe and young forever?
Do you remember when I mentioned that the study did not adjust for income? That part is important. There is a well-recognized inverse relationship between income and obesity in women in America.
Let’s start with The New England Journal of Medicine, in “Obesity and Socioeconomc Status — A Complex Relation.” NEJM, Volume 329:1036-1037, September 30, 1993, Number 14. The abstract for this editorial states:
One of the most striking facts about obesity is the powerful inverse relation between obesity and socioeconomic status in the developed world, especially among women. What is responsible for this association? There are at least three possibilities: obesity influences socioeconomic status, socioeconomic status influences obesity, or a common factor or factors influence both obesity and socioeconomic status. There is evidence to support each of these possibilities, and limits to the evidence for each.
The editorial observed that multiple studies demonstrated the link between socioeconomic status and obesity, but the cause was more complex, also including heredity and other factors. While socioeconomic status had a clear effect on obesity, obesity also had an effect on socioeconomic status, as the obese suffered a social disability, and loss of income, for their weight. The purpose of the editorial was to encourage doctors to treat their patients without prejudice, to address the symptoms without adding to the list of “horror stories” about treatment by insensitive physicians.
We can see a more detailed, and more modern, study in Age, Socioeconomic Status, and Obesity Growth, Baum and Ruhm. They, too, found that “adult body weight and obesity are inversely related to social and economic advantage.” Id. It is actually quite complex, not a simple straight line money/weight analysis, in part because obesity itself generates a “weight penalty,” reduced wages for increased weight. The conclusion, though, is pretty straight-forward, “excess body weight is inversely related to socioeconomic status at all observed points of the lifecycle and these disparities increase with age.” In other words, the more money you have, the less likely you are to be obese.
Can we take a look at wine consumers, now? I will use, as a proxy, combined demographic data from more than forty wine websites, collected among The Palate Press Advertising Network‘s network of more than 70 different wine websites. What do we find? First, we find that wine readers, and presumably wine drinkers, are more affluent and more educated than average, and have fewer children in the household. The “Index” on the graph is a comparison the internet average. An index of 100 would mean the measure is identical to the internet average, while an index of 133 would mean 33% above the internet average. These measures come from Quantcast.
Remember, the study everybody is talking about did NOT adjust for education or income.
So what do we conclude from the study? Perhaps something significant, that red wine helps women keep weight off. But it is more likely we are merely rediscovered something we already knew, that the poorer and less educated you are in America, the less likely you are to be healthy.