Thanks for the post, and yes I believe SAD has alot to do with how bodies function. But I also believe it is learned behavior by our bodies. I think it outsmarts us with its own memory, constantly readjusting and putting a stop to something it feels threatened by. I think that explains why one doesn't have the success in a second try of any plan as the first time.

If SAD were really a factor though, I wonder why. If it is a defense mechanism from early neander days, why it doesn't hold true for all humans.

All the factors stated somewhere or another are valid reasons, yet we are with our histories all so different that one wonders how to ever find out what makes our individual case tick.
Just why any doctor than could prescribe one diet over the other for instance is a puzzle to me. And what do they then tell people like turtles and stallers, that they are not trying hard enough ?
Where is the scientist that tells it how it is. We just don't know the answers yet. Just marvel at this body for being able to adjust and survive. Now if that would only work for the mechanic parts as well...wow we all would be so much better off.

thanks again for you post and YES I will see if there comes a difference. will be interesting to see.