I got this little tidbit of info from Shape Magazine. It was an article written by Alla Byrne called "Exercise advice from Jessica Simpson's Trainer"
“You can have the greatest trainers in the world get together and devise a workout plan for you, but if you only do it once a week, you’re not going to get the same results as someone who works with a mediocre trainer, but exercises four days a week. Also, the more consistent you are with your workouts, the less intense your sessions have to be. And again, diet is very important. I think people start to work out and they see it as an excuse to eat whatever they want. Sadly, that’s not the case.”