Sigh!  ^_^

http://www.nytimes.com/2007/05/08/health/08fat.html?em&ex=1178856000&en=271d386f
02040361&ei=5087%0A

EXCERPTS

Every time the result was the same. The weight, so painstakingly lost,
came right back. But since this was a research study, the
investigators were also measuring metabolic changes, psychiatric
conditions, body temperature and pulse. And that led them to a
surprising conclusion: fat people who lost large amounts of weight
might look like someone who was never fat, but they were very
different. In fact, by every metabolic measurement, they seemed like
people who were starving.

...

The Rockefeller researchers explained their observations in one of
their papers: "It is entirely possible that weight reduction, instead
of resulting in a normal state for obese patients, results in an
abnormal state resembling that of starved nonobese individuals."

Eventually, more than 50 people lived at the hospital and lost weight,
and every one had physical and psychological signs of starvation.
There were a very few who did not get fat again, but they made staying
thin their life's work, becoming Weight Watchers lecturers, for
example, and, always, counting calories and maintaining themselves in
a permanent state of starvation.

...

The implications were clear. There is a reason that fat people cannot
stay thin after they diet and that thin people cannot stay fat when
they force themselves to gain weight. The body's metabolism speeds up
or slows down to keep weight within a narrow range. Gain weight and
the metabolism can as much as double; lose weight and it can slow to
half its original speed.

...

The message never really got out to the nation's dieters, but a few
research scientists were intrigued and asked the next question about
body weight: Is body weight inherited, or is obesity more of an
inadvertent, almost unconscious response to a society where food is
cheap, abundant and tempting? An extra 100 calories a day will pile on
10 pounds in a year, public health messages often say. In five years,
that is 50 pounds.

...

Dr. Stunkard ended up with 540 adults whose average age was 40. They
had been adopted when they were very young - 55 percent had been
adopted in the first month of life and 90 percent were adopted in the
first year of life. His conclusions, published in The New England
Journal of Medicine in 1986, were unequivocal. The adoptees were as
fat as their biological parents, and how fat they were had no relation
to how fat their adoptive parents were.