Red wine has a whole bunch of health benefits − hurray for that! But too much and it could be adding to your waistline. Besides the extra calories and sugar in those glasses of wine, drinking too much also slows down your metabolism. When you have a glass of wine (or beer, or liquor), your body has to break down the booze before it can break down the calories you consumed during the day. That shows down your metabolism, leading to weight gain. So limit yourself to a glass of wine a day.