Alcohol is a really good energy source and it the first thing your body will try to metabolise. So when you are drinking beer your body turns the alcohol into energy, then after you're sobered up a bit starts on the sugars and then carbohydrates. The chips you ate (starches and fats) aren't needed for energy right now and so are stored away for later (as fat).
The traditional "beer gut" is actually an enlarged liver - no that's not a good thing, it means it's stressed.
So no, it's not the beer, it's the food you eat while drinking. Eat well before a drinking session, don't eat crap food during. Drink plenty of water before bed and get some exercise occasionally!