People go on low carbohydrate or ketogenic diets and feel better because cortisol and adrenaline levels are boosted. It's like getting a cortisone shot. This affect can last a year or two. But then eventually stress hormone resistance develops and the whole thing falls apart with some ugly health consequences. People get crashed testosterone and thyroid levels and brain fog.

Sustained low carb is a bad idea. You are mimicking the metabolism of starvation. For the most part you want to be operating with glycogen topped up.