Low-carb is not "new", it is just that it fell by the wayside for a long time and people have recently caught onto it again. It was around more than 30 years ago. It was just then people didn't have a clue as to the fact that some fats are better than others. (They were still cooking their baked goods using lard ).

Your brain is the only part of your body that truly needs glucose in order to function. The rest of the body can use ketones (the product of fat breakdown) as its source of energy and very quickly starts using them as soon as you go on this type of diet. There are plenty of low-carbo veggies out there that you can use as a fiber source.

If these concepts were not true, then everyone that has tried lo-carb dieting would be dead by now, having had no energy source in order to survive.