Cereal and Bananas mean a Boy?

A recent AP article "Mom's diet seen as factor in whether baby is boy or girl; could cereal, banana mean a boy?" suggests that the sex of the baby can be guessed by the caloric intake of the mother. One of the nonsensical arguments the scientists put forth was that embryonic boys take up more nutrients than girls ("It just might be that it takes more nutrients to build boys than girls, he said.").

However, because the reproductive rate of men is greatly increased by physical fitness, while the reproductive rate of women may not increase much (in each case, assuming that he or she is healthy enough to escape mortality), it makes sense for a mother to improve the health of unborn male offspring over herself moreso than unborn female offspring.

Another question, which it does not appear that they answered, was whether higher caloric intake by women could cause a higher chance of male offspring. That should be easily noticed on a country-by-country basis, as calorie intake has generally increased globally. However, I would doubt that would make much of a difference -- otherwise, successful populations would have found their populations favoring males, which reduces birth rate and increases internecine conflict.