I remember reading a study in the Weekend Australian magazine years ago about weight loss. It was an Australian study, though IIRC there were international participants. One finding around the weight loss was that when people had lost a significant amount of weight, for months and even sometimes years afterwards, their bodies still reacted in certain ways as though they were still obese. Their bodies actually somehow tried to keep making them put weight back on. I remember there was one lady who found she had to exercise something like 6 hours per day to keep her weight loss off. I can't remember much more than that, but I found it fascinating to learn how the body - at least as far as this study claimed - fought you on weight loss. People are so often criticised for having low will power when they regain weight, but maybe that's not the complete picture.
On a more anecdotal note, in talking to a friend whose parents migrated from Italy, she does not experience the bloating/fullness sensation that I feel from eating pasta. Is there something to be said about her genetic influences coming from Italy??
I've heard similar anecdotes from relatives, with someone of Norwegian heritage marrying someone of Sri Lankan heritage, and as they compared how their bodies reacted to various food types, found they were quite different, and attributed those differences to the traditional foods of their (or their grandparents') home countries.