Well, I've been playing with my diet for a while now (more than 3 years).
It started 4 years ago, when I started having digestive problems.
After some doctors, studies and pills (which didn't solve or find anything), I started modifying my diet (adding some veggies).
I used to eat no veggies at all.
I started reading info in the internet, etc. And I became really regular with the meals, not focusing so much on taste or sociability but on the effect food had on me. Not only my digestive problems resolved, but I found a lot of other things that diet solved.
This was all part of a bigger change in my life that took place before that time (which includes meditation).
Long story short, I removed seeds, added more oatmeal with blueberry juice (only blueberry juice) and some of cocoa powder (good quality), and cut back on legumes (I was eating a lot).
I think the "secret ingredient" is cocoa powder (in the context of my low fat vegan diet).
I started noticing the effects on my neck the first two weeks. Around three weeks my sleep had improved.
I noticed I was more relaxed. While they hurted, I noticed that I could stretch my legs more. I could sit in lotus and place both knees on the ground (I've been trying to do that for 2 years....).
Some releasing of pressure in my head also made senses a lot more "real". My posture improved. I have more confidence, etc.
In yoga I started being close do to poses that I couldn't even attempt to do.
It's important to note, however, that I can't relate this change to meditation. They are physical, and while they had great impact in my life, they do not compare to paths. I think paths are better

I'm still 2nd path and the breakthrough is not related to meditation.
However, if I keep my diet (which I'll do), I can't help think what will happen when I release the knots in the back of my head (some have been released) and the crown, etc.
Also, if I'm able to sit for longer periods, or other things.
Finally, I don't know how to integrate this with the stages.
I'm convinced that regular activities, like what you eat, what you think, your work, your emotions, etc, have a profound effect on meditation. I'm also pretty sure that to meditate to escape all those things is a bad idea. Isolating meditation from those things is a bad idea.
Daniel talked a lot about his efforts to meditate while being ill.
MCTB also talks a lot about "jaw, neck, back, etc".
Maybe this "relaxing" stabilizes (doesn't seem so). Maybe it's dangerous and I'm ruining my health (I faced that fear some time ago

).
Maybe this helps me get 3rd or 4th path. Maybe it hinders my meditation.
My blood pressure dropped from 110/70s to 100/60s - 90/50s. While I haven't been feeling dizzy, I wonder if that is too low.
Like I said, physical, measurable changes.
So far, it seems to have only positives, but you never know. I'll be careful.