I adopted a low carb, and then 6 years later a gluten free diet.
My low carb goal was "don't trigger your insulin - because it's a defensive mechanism".
I followed the information on dietdoctor.com (without paying) and their visual food guides are excellently simple.
Mood and foggy brain mostly cleared up and massive improvement in emotional stability.
My weight went from 83kg down to 76kg - which was great / ideal.
Then went gluten free a year ago. (as I was previously having some toast and biscuits).
(apparently) If gluten gets through your gut wall (Which it will if you have a mild intolerance that isn't enough for a medical diagnosis), you might have caused yourself a dairy intolerance, and it also Turns out gluten binds to your neuroreceptors, including dopamine receptors - which means you will not really register dopamine and therefore can't be happy - you just feel flat. or "Meh". If you feel this way after a bloaty big pasta meal - I'd seriously recommend testing yourself by going gluten free for a month and see how you feel at the end of it.
For me - my mental cognition and speed has returned to the clarity I had when I was late twenties (this alone is just seriously fantastic), I have excellent emotional stability (no "Meh"), my brain is fantastically capable again, and I've got down to my perfect weight of 70kg. and the real magic is my gut health is phenomenal. Truly didn't know this was possible.
In the same way we feed our pets a different diet into middle age, we should as humans consider it.
Apart from the obvious avoidance of diabetes type2, a low-carb, high-fat, zero-gluten diet is incredibly easy to follow, very tasty, and exceptionally healthy.
Side bonus - my heart tachycardia stopped after a month of no gluten - so clearly some neuroreception improvements - my cardiologist has stopped all treatments.
Gluten free is easy now thanks to the introduction of "genius" branded bread - which is actually like bread, not dust sponge, and therefore sandwiches and eggs on toast can be a thing again - just as long as you don't trigger your insulin ;-)
I challenge anyone to the low-carb & gluten free diet for a month and tell me you're not feeling better for it. Eat what you like - don't trigger your insulin. Simple.
(more information about low carb and diet also from the Zoe ZOE—Understand how food affects your body
website - it's all very personal)