Is it legal to tell employees to lose weight?

Q. "The father of the company's owner approached a few employees to discuss weight-loss, provided them with materials on how to lose weight and told them to speak with her subordinate about the issue. Is this illegal? The employees in question interact with customers on a daily basis and believe this is implying that they must lose weight to keep their jobs. No other overweight employees have been approached about this, which enforces the belief that only employees interacting with customers are being targeted." – Anonymous, Texas