Prolonged restriction without resistance training of some kind may lead to a loss of lean muscle tissue. If you're going to do intermittent fasting, it's best if you're on some kind of regular lifting program. If you are lifting and fasting, you won't see any muscle loss. There's research in that area as well. You'll probably even see increases in strength. I have. If you're really interested in the topic, check out Eat Stop Eat. Lots and lots of cited research in his book. Wouldn't that defy the idea that maintaining a caloric deficit is the primary cause of weight loss? (And as a follow-up, that generally speaking it is almost impossible to lose fat while maintaining 100% of your muscle mass?) Not trying to stir trouble, just interested in your thoughts.