Now beer has to be low calorie. Its mostly water and grain after all, with a few hops for flavouring.
Where is the harm in that.
Quick check on Google and the calories contained in malted barley more than account for where the calories in beer come from.
Seems to me that some are actually lost somewhere between malted barley and a pint of beer.
Bottom line. Malted barley is very high in calories.