I have been part of the CrossFit community for a while now and there is one fact that is undisputable; without eating a diet to sustain health and fitness and NOT fat, you will not see results. You just won’t. An athlete does not eat as you and I; their macros and micros are carefully calculated on their body weight and specific sport regime.
What we can do, us mere mortals, is care, really care, about the quality of food that we do eat. This is true for children and adults alike. I have worked with teenagers in Pastoral Support and I can promise you, I can tell the difference in behaviour of a young person who ate a healthy breakfast compared to the one who drank ‘Monster’ or ate nothing at all before school.
We need all 3 macros, any diet that has you cutting out one or more of the foo groups above is literally a fad, one you cannot and should not sustain.
If you want to see results in your health, fitness, focus and attention, then you must eat and train for them. It really is that simple.