That comment from Jenny Ruhl has stuck with me too (she develops it more in her book Diet 101) - bascially low carbers eat both high fat AND high carb when they go off the low carb diet. I know that's true for me, and I think it's contributed to the speed of regain when I've gone off the rails in the past 5 years.

But I also agree that good-quality fats are good for kids, and I don't feed my 2 kids low carb but they do get plenty of fat, including quite a bit of saturated fat.