Well, yeah, duh
They had to research that? The Greeks knew it 2500 years ago! "A sound mind in a healthy body." Derived from the aphorism, "Νοῦς ὑγιὴς ἐν σώματι ὑγιεῖ".
Tell me again - what's the supposed benefit of getting rid of school Phys Ed classes?
I've also noted for myself that eating whole natural foods helps me feel clear of mind and be able to problem solve better and to remember things better than when I eat a lot of processed foods. Hmmmmm, treat your body right and it treats you right.... Who'd have thunk it?