New genetic research helps explain why, despite people's best efforts, obesity can be hard to fight.
Why is it that some people do not manage to lose weight despite their best efforts, while others can eat whatever they please and stay thin? The answer, suggests a new study, may be genetic.
Sadaf Farooqi, a professor at the Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge, United Kingdom, led the new research, which compares the genetic makeup of people who are overweight with that of people who are thin.
To the authors' knowledge, this is the first time that a genetic association study has also examined thin and healthy individuals.
Prof. Farooqi and her team analyzed the DNA of 14,040 people in total and published the results of their analysis in the journal PLOS Genetics.
Obese people have a higher genetic score
The researchers took DNA samples from 1,622 thin participants, 1,985 people with "severe early-onset obesity," and a further 10,433 control participants whose weight was within the normal range.
About 74 percent of people in the thin cohort had family members who were persistently thin.
In their analysis, the scientists found genetic variants that previous research had already linked with obesity. They also identified new associations between specific genetic loci and both severe obesity and thinness.
The researchers generated a "genetic risk score" from the 97 genetic locations relating to a person's BMI.
Study co-author Inês Barroso, who is the leader of the Metabolic Disease Group at the Wellcome Sanger Institute in Hinxton, U.K., reports on the findings.
She says, "As anticipated, we found that obese people had a higher genetic risk score than normal weight people, which contributes to their risk of being overweight. The genetic dice are loaded against them."
The study also found that slim individuals had a significantly lower genetic risk score. "This research shows for the first time that healthy thin people are generally thin because they have a lower burden of genes that increase a person's chances of being overweight and not because they are morally superior, as some people like to suggest," Prof. Farooqi explains.
"It's easy to rush to judgment and criticize people for their weight, but the science shows that things are far more complex. We have far less control over our weight than we might wish to think."
Prof. Sadaf Farooqi
The researcher also explains how the findings may lead to new therapies for obesity. "We already know that people can be thin for different reasons," she says.
"Some people are just not that interested in food whereas others can eat what they like but never put on weight. If we can find the genes that prevent them from putting on weight, we may be able to target those genes to find new weight loss strategies and help people who do not have this advantage."
In the United States, almost 40 percent of the adult population, which equates to more than 93 million individuals, have obesity, according to the Centers For Disease Control and Prevention (CDC).
Maintaining weight loss is a difficult task for most, with some studies suggesting that 50 percent of people who manage to lose weight return to their original BMI within 5 years.