I am getting my personal trainer certification also, and most folks want help with their eating habits, too, so the two go hand in hand.
I'm not crazy about the Jenny Craig concept, because you lose weight eating her food. People need to learn to eat from the grocery store in the real world. Then they can maintain their weight loss better. I wouldn't mind working for Weight Watchers, however, if I were looking for that type of job. Their program I DO like.