text: fitness classes which are the best? which would be the best exercise  to lose weight fast and tone up in five months,yoga or aerobics (sorry about the spelling)i need to lose 2 and a half stone please help. aerobics as it raises the heart rate to burn fat start with something simple and expand the style of the class as you start to lose weight and become more confident, if it's the first time you have done it you will feel body conscious and if you have two left feet like me ( and i teach aerobics) you will have a great laugh and every instructor likes a challenge it makes every day different. good luck