Scientists identify obesity gene

British and French scientists have identified several variants of a single gene that boost the risk of obesity, according to a study published Sunday in the British journal Nature. Previous research had shown that an extremely rare mutation in the same PCSK1 gene can, all by itself, lead to huge gains in weight, making it the only known source of so-called "monogenetic" obesity.
But a team led by Philippe Froguel of Imperial College London wanted to find out if PCSK1 might lead, in combination with other genetic factors, to more complex and widespread forms of obesity as well.
When they compared the genomes of 13,000 obese individuals of European ancestry to those of a normal control group, the researchers found three mutations in the gene that were far more common among those coping with excess weight.
These same variants were also linked to increased risk of childhood obesity, as well as less extreme weight gain, the study found.
The benchmark for obesity is the body-mass index (BMI), defined as one's weight in kilograms divided by the square of one's height in meters.
A BMI from 18.5 to 25 is considered in the healthy range, from 25 to 30 is overweight, and 30 or higher is obese.
PCSK1 produces an enzyme, called proconvertase 1, that plays a critical role in converting inactive forms of hormones that control appetite and regulate energy metabolism into active forms.
These hormones include insulin and glucagon, involved in the metabolism of sugar and carbohydrates, as well as a third molecule that signals to the brain that one has eaten enough.

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