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Some Cold Statistics About Birth Date and Weight

March 06, 2000|ROSIE MESTEL

What's your sign? From the International Journal of Obesity, we learn that someone's birth date may really may make a difference in their weight as adults--but not because of any of that astrology stuff.

David Phillips, an epidemiologist at the University of Southampton in England, and Dr. Jim Young, an endocrinologist at Northwestern University in Chicago, found that people born in the first half of the year were more likely to be obese as adults than those born in the second six months.

The two compared the birth weights and current weights of 1,750 English men and women born between 1920 and 1930. They found--remarkably--that while 12.7% of the men born in the months January through June developed obesity (with obesity defined as a body mass index of above 30) only 9% of the June-to-December men went on to do so. There was a similar trend in women. (Speaking as someone whose birthday falls in February, I don't much care for this finding.)

The scientists also compared people who were born in January through June following a cold winter with those born after a mild winter. Cold-winter babies, they found, were more likely to be obese as adults than those who were born following a mild winter. Thus, they suggest that cold temperatures around the time of birth could be behind their finding. (Remember all those chubby ladies painted by the artist Peter Paul Rubens? Is it a coincidence, asks Young, that Rubens painted during a chilly period of history known as the Little Ice Age?)

But wait a minute--isn't it pretty cold in November and December? True, says Young. It's possible that something else--such as the length of day or amount of sunlight--is exerting some mysterious influence on our physiology.

In favor of the temperature hypothesis, Young points to prior experiments of his that used rats as test subjects. Rats raised for the first few months of their lives at colder temperature end up bigger and chubbier than rats raised under warmer conditions. I'm guessing it was a hard, hard winter the year my cat Jack was born.

In Search of Some Signs of Strength

Body weight, meanwhile, isn't the only human trait that has a season-of-birth effect. In an article called "Like a Virgo" from the British magazine New Scientist we learn:

* Scientists found that English professional soccer players in the 1991-92 season were almost twice as likely to have been born between September and November as during summer months.

* Two European studies found that more medical students have birthdays between April and June than would be expected by chance.

* An Austrian study reported that men born between March and May were on average 6 millimeters taller than men born between September and November.

* Scientists who were quick to accept radical new ideas such as evolution and the theory of relativity tended to be born between October and April.

* Rates of conditions such as schizophrenia, diabetes, manic depression and allergies have also been reported to vary with month of birth. Again, scientists don't know why but wonder if certain viruses may be more likely to infect pregnant women at certain times of the year.

And in what month are most people born? According to "Like a Virgo," birth rates spike in September, "usually blamed on people getting carried away at Christmas and New Year's festivities." Prolonged power outages and labor strikes by electricity workers also contribute to birth spikes nine months later.

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