A huge real ale festival opens with new research claiming that beer can help people lose weight - when drunk in moderation.The Campaign for Real Ale (Camra) said a third of men and women wrongly believe that beer has more calories than other alcoholic drinks.Swapping wine for beer for just one week would save as many calories as a half-hour jog, Camra claims.Chief executive Mike Benner said: "It is great news to see the myth of the beer belly finally laid to rest. The main message we are putting forward today is that, as a low-alcohol drink, beer can supplement a healthy lifestyle if consumed in a responsible manner."