Low-fat and low-carb aren't myths. They're just styles of eating that focus on different macronutrients.
Basic biochemistry dictates that there is no physiological need for dietary carbs. Of course, it is impossible to completely eliminate carbohydrate in the diet — there's a little bit in everything we eat. But our body can generate all the glucose it needs from the protein and fat we put in. The same can't be said for amino acids or fat, so they become the essential macronutrients.
I do agree though that there's no one-size-fits-all diet. Figure out what works for you. If you fare well on 50% carbs, congratulations. I just get cranky on that same amount.
1) eat real food - more vegetables, moderate meat, moderate fruits, less grains, less sugar, less vegetable oils.
2) exercise - moderate intensity cardio, sprinting, heavy lifting, dedicated stretching and mobility.
3) live - relax, de-stress, meditate.
Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).