“Researchers and public-health officials have long
understood that to maintain a given weight, energy in
(calories consumed) must equal energy out (calories
expended). But then they learned
[5] that genes were important, too,
and that for some people this
formula was tilted in a direction
that led to weight gain. Since the
discovery of the first obesity gene
[10] in 1994, scientists have found
about 50 genes involved in
obesity. Some of them determine
how individuals lay down fat and
metabolize energy stores. Others
[15] regulate how much people want
to eat in the first place, how they know when they’ve had
enough and how likely they are to use up calories through
activities ranging from fidgeting to running marathons. People
who can get fat on very little fuel may be genetically
[20] programmed to survive in harsher environments. When the
human species got its start, it was an advantage to be
efficient. Today, when food is plentiful, it is a hazard.”
http://www.nytimes.com/2006/08/13/magazine/13obesity.html.
In the text, the central idea is that
