Hello. Forgive me if this is the wrong section for this thread, and if so please feel free to move it. (Also please note that I mean no offense to anyone at all with anything in this thread.)

So I'm just wondering, I've commonly read and hear that one of the biggest factors in someone's overall mental (and cognitive) function/health is diet, and if you have a poor diet your mind is going to suffer and vice versa if you have a healthy diet your mind will be healthy.

But if this is true and such a significant factor, I just don't get how there are plenty of very, very, and even very overweight people, who function mentally/cognitively just as good or even better than somebody who has a very healthy diet, or just a normal not healthy but not unhealthy diet.

I get that there are many other factors too besides diet, but from what I can tell, and have read and heard, diet is one of if not the biggest most considerable factors, so if that's true like I said I just don't get how an (no offense intended) obese person who eats nothing but junk food constantly, can mentally/cognitively function just fine or even better than others with a better diet.

Edit: I thought of a good example. My father isn't overweight or anything - but his diet isn't the best, and he eats a lot of little Debbie's and sweets, and he functions perfectly fine, and I'd say mentally even 'sharper' than hardly anybody else I know, yet sugar is supposed to be one of the worst things for your brain even.