When summarizing the recent scientific evidence, it seems that light to moderate consumption of alcoholic beverages is less likely to be a risk factor for obesity than heavy drinking and binge drinking.
Since one gram of alcohol provides 7.1 kcal (29 kJ) and alcoholic beverages can be considered additive to the energy intake from other dietary sources, it is widely believed that even moderate drinking promotes a positive energy balance leading to weight gain and ultimately to obesity. However, studies on this topic have shown conflicting results. To gain the best available evidence and to provide an update on the link between alcohol intake and obesity as well as on factors that may explain the conflicting findings, Canadian researchers reviewed the literature and published a critical review.
Observational studies examining the effect of alcohol intake on obesity date back almost 30 years and have been carried out across small and large study groups, in many countries, across various ethnicities and age groups. The Canadian researchers found that since 2005, the majority of cross-sectional studies (*) have demonstrated no significant association between frequent light to moderate consumption of alcoholic beverages and obesity risk. Heavy drinking and binge drinking, however, were more likely to carry an association with excess body weight. Also the intake of alcoholic beverages by older adults was more likely to be associated with overweight and higher body fat. But as the scientists stressed, such cross-sectional studies are unable to prove a cause-and-effect relationship. The results of prospective observational studies are thus more informative.
In their review, the scientists concluded that the most recent prospective studies suggest no association between light-to-moderate consumption of alcoholic beverages, general weight gain or gain in waist circumference. Heavy drinking, however, has been more consistently associated with weight gain and increases in alcohol intake patterns appear to promote weight gain.
The best available evidence to prove cause and effect comes from experimental evidence. The studies reviewed in by the Canadian scientists suggest that moderate intake of alcoholic beverages does not lead to weight gain, even though they stress that the intervention
periods in those studies ranged only from 4–10 weeks, and therefore may not have been long enough to identify the slight changes in weight that can accumulate over time to result in overweight or obesity.
When reviewing the many factors that could possibly explain the conflicting findings, the authors stressed that confounding could be involved and individuals who frequently drink moderate amounts of alcoholic beverages may enjoy a healthier lifestyle in general which may protect them from weight gain.
Traversy G, Chaput JP. Alcohol Consumption and Obesity: An Update. Curr Obes Rep. 2015;4:122-130
For more information about this article, read the scientific abstract here.
(*) The defining feature of a cross-sectional study is that it can compare different population groups at a single point in time.
Longitudinal Study: in a longitudinal study, researchers conduct several observations of the same participants over a period of time, sometimes lasting many years. The benefit of a longitudinal study is that researchers are able to detect developments or changes in the characteristics of the target population at both the group and the individual level. The key here is that longitudinal studies extend beyond a single moment in time.