Yes, too many radio personalities are overweight, because they have nothing to do but sit behind a microphone all day. The people on the radio know that no one is ever going to see them, so they don't have the incentive to take care of themselves like the people on television do.
A radio personality does not have a physically demanding job. Their work is not going to require them to use equipment that requires a specific weight restriction, nor are they moving around much at all. Firing someone based on their weight is discrimination and should be protected. Without basic protections such as this, overweight people could find themselves in a very bad place in the employment marketplace.
I think that no one should be fired based on weight and that it is a prejudice. If someone else weights more then they should it is no ones business but their own. You never know if there is a health problem or the reason they are that way. His weight should have nothing to do with how he perfroms his job.
I'm not quite sure how being overweight would affect how a radio shock jock does their job or why it would even matter. The job involves sitting for long periods of time, so it does make sense why radio DJs would tend to be heavier than the average person, but I don't think there is a trend of obese radio personalities.