At the BA interview, you are required to sit and and strap into a jumpseat, then assume the brace position. This was introduced when some people in training were failing because they couldn't strap in. There were also a couple of people on line that had problems too.
sam.lk7, you're speaking from an aussie point of view, in the EU there is very tricky anti-discrimination employment legislation regarding weight. Some airlines may specify 'weight in proportion' but they leave themselves open to potential lawsuits.