Candy Maree, it's a myth your brain needs carbs to function. Happy to publish as many peer reviewed studies as you like debunking this. Your brain can, and does, do very well in a ketogenic state. I suggest you read
The Art and Science of Low Carbohydate Living by Volek and Phinney who are scientists leading the way in the field of nutrition and metabolic study
Dr Layne Norton also has some very interesting published works, also very respected in the field. There is a difference to low carb diets and no carb diets. Most low carbs are still getting a realistic amount of carbs through fruits and vegetables. Please note, I did say don't eliminate them. I'm more than happy to read additional works, and enjoy doing so in order to read other people's opinions.

Either way, Diet is still key. You can't out exercise a bad diet.