"Is your size holding you back?"

You magazine with the Mail on Sunday has an article in it today called "Is your size holding you back?", which has been retitled on their website to: Are you too fat to get a good job? (Presumably their website readers wouldn't have understood the nuances of the original title). In it, it says:

Studies suggest that weight discrimination in the workplace is rife.
A recent survey for Personnel Today magazine revealed that 93 per cent of human resources (HR) professionals would give the job to the thinner person when choosing between two otherwise similar candidates, and the evidence suggests that weight discrimination counts more against women.

Overweight workers were routinely stereotyped as 'possessing negative personality traits', and dismissed as 'emotionally impaired'. Overweight people are typically seen as lazy, out of control, even dirty.

And apparently, very thin people don't get off well either:

"I would be wary of a candidate at an interview who was obviously smaller than size eight," agrees a (female) blue chip company HR director who did not want to be identified. "To my mind, a woman that thin has a problem, or at least an unhealthy attitude to food. In my experience, people like this don't make good team players and tend to be introverted and self-focused."

I would hope that I would always pick the best candidate, regardless of sex, religion, ethnicity and size...but how can I be absolutely sure that I'm not secretly sizist?