So, assuming you are NOT a type II diabetic, what is the optimal number of grams of carbs to consume to burn fat, or to maintain weight?
The Mark's Daily Apple web site has a very interesting graphic, called the Primal Blueprint Carbohydrate Curve. (The author of this web site, Mark Sisson, is also the author of the book The Primal Blueprint, which extols the virtues of a Paleo diet like our caveman ancestors used to eat. It is not necessarily the same thing as a low carb diet, though it is very similar. I will do a post on Paleo diets one of these days).
In this carbohydrate curve, optimal fat burning happens when you are in ketosis or when you engage in intermittent fasting, which means you consume 0 to 50 grams of carbs per day. The "Weight Loss Sweet Spot" is 50 to 100 grams of carbs per day. Effortless weight maintenance is 100 to 150 grams of carbs per day, and anything over 150 grams will contribute to weight gain.
Again, this is NOT for type II diabetics. When I finally lose my weight, I will have to see how carbohydrates affect my blood sugar before adding them back, but I do think this is a useful rubric for weight loss and weight maintenance down the road.