As a certified nutritionist, NSCA certified strength and conditioning expert and practicing sports medicine MD, I fully support intermittent fasting but do not encourage people who are physically active in jobs requiring heavy labor and equipment operations or endurance athletes to starve themselves during the day. There is no reason to create an unnatural window of fasting during the day. By simply shutting down the metabolic factory at 8pm and opening back up at 8am the next morning…voila!…you get a 12 hour fast that promotes a natural uninterrupted sleep by reducing activity in the GI tract. An important point advocates of intermittent fasting often neglect to address is that the fed state is associated with a more pleasant mood and the starved state is characterized by hangriness and irritability. You cannot function in a customer relations driven industry with a starvation induced negative mood.