Hmm, I haven't heard that theory, about the varied diet. I know when I got pregnant with DS, I had just finished yoga teacher training and was eating super healthy. I had a super easy pregnancy with him. Not one second of morning sickness. I had no cravings or food aversions. It was a pretty amazing and easy pregnancy, aside from being persistently breech and requiring a c-section. So, trade-offs?
With DD, I wasn't exactly as super fit and eating as wholesomely as I was when I was pregnant with DS. Also, I was still nursing. I had serious chicken aversions while pregnant with her, but I did crave really good hamburgers. I also wanted sweets, and conversely spicy hot wings and salt and vinegar chips. And cherry icees.... Oddly... I gained less with DD than with DS! I also had mild to moderate morning sickness.
This time, I don't know the sex and we're waiting to find out but it has been the hardest pregnancy so far in terms of horrible and constant nausea. I have more food aversions, although I can now tolerate chicken - but only if its seriously minced up with a bunch of other stuff - and that's only been in the last couple weeks. I also want hamburgers again. And pretzels (but I think that is because I am trying to quell the nausea). I was not out of shape, but I wasn't eating as super healthy as I was when I got pregnant with DS, although I do cook at home almost every night. I was also still nursing (am still nursing) DD when I got pregnant.