Based on the fact that the energy content in 1 gram of alcohol is 29 kJ or 7.1 kcal, excessive alcohol consumption has been linked to weight gain.
However, based on their review, the scientists conclude that, “as positive associations between alcohol and weight gain were mainly found in studies with data on higher levels of drinking, it is possible that an effect on weight gain or abdominal adiposity may only be experienced by heavy drinkers.”
A second conclusion of the authors is that “the type of alcoholic beverage might play an important role in modifying the effect of alcohol consumption on weight gain,” with more favourable effects generally seen among consumers of wine.
The overall conclusions of the authors is that it is currently unclear whether alcohol consumption is a risk factor for weight gain, but if so it appears to occur mainly among heavier drinkers. They also state that “light—to—moderate alcohol intake, especially of wine, may be more likely to protect against, rather than promote, weight gain.”