Someone who goes from daily alcohol drinking to stopping altogether can expect to see physical body composition changes as well as weight loss in the days to weeks after they quit drinking alcohol.
After a fortnight, you are also likely to start losing weight as a result of giving up alcohol's empty calories. If you were to stop drinking six 175ml glasses of wine per week, you would have saved 1920 calories at this point, and 2160 if you'd stopped drinking around six pints of lager.
Even if it is a light beer, that is approximately 100 calories per day. Over 1 week, that equals 700 calories. When looking at cutting out that 1 beer each night over an entire month, that would eliminate over 3000 calories. Someone who drinks 3-4 beers per day would be looking at 9000-12000 fewer calories per month.