Following on from the posts, many airlines now look to the personality and experience rather than weight. The airline I work for are looking for people who are able to handle the situations, ability to work under pressure and are adaptable.
As for weight, we use the phrase 'height to weight ratio'. This means that you should be able to carry your weight for your height. The only test they will do if they think that you may be too large is to ask you to sit on a crew seat and fasten the belts. You have to by CAA regulations sit in a crew seat and fasten the belts without any problems.
If the job is the one you want, then this should be an incentive to be of a weight that you would be happy with and for your own health...you don't have to be thin or glamarous for this job, a smile and determination will get you further.
Good luck.