If I go on the atkins or caveman diet, will I lose weight? I don't want to lose weight, but improve my brain?

If you consume the same amount of calories that you do now on these diets you won't gain weight since your taking in the same amount of energy. When your on this diet you don't eat foods that contain gluclose, which your brain needs, so slowly your body starts turning the protein and fat you eat into fuel for your brain called ketones. When this happens your brain gets used to running on this you might feel a little sluggish for a few days but I've been on this diet for 8 months and after three weeks I was back to normal.