I'm not sure how familiar you are with the way the marketing process works. With humans, the pharmaceutical reps used to visit hospitals and large medical practices and bring food and all sorts of promotional material (pens, mugs, etc.) and provide research information about how wonderful their drug of the month was. MDs that were top prescribers would be asked to give lectures at other places that were quite lucrative or there would be all sorts of lovely trips prescribers could be invited to attend free of charge. All you had to do was listen to the drug company's spiel. Quite a few years ago, the FDA put a stop to the promotional practices of Big Pharma. There are no such preventative measures that govern the pet food industry. However, a few years there was a rather large class action suit that the pet food industry lost. As Bron noted, the suit prevents them from calling their food "prescription" since there's nothing medically prescriptive in the food. I really doubt that many of the vets are aware of the suit. In fact, most vets don't know what the carb level is in most foods. They trust the pet food company. My vet was completely clueless that Fancy Feast was far lower in carbs than either the Hills or Purina diabetic foods.
