New genetic research helps explain why, despite people's best efforts obesity can be hard to fight.
Everyone who has tried to lose weight will be familiar with the frustration that often accompanies weight loss efforts. Sometimes, it may seem as though people who are overweight are fighting a losing battle, while slim people can eat whatever they want. New research suggests that this may be true - at least from a genetic standpoint.

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.

As the researchers explain, genetic association studies so far have focused on people who are overweight, as well as zooming in on body mass index (BMI) and obesity.

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.

Comment: Understanding obesity: Replacing bias with curiosity
You may not be able to change your feelings, but you can practice changing your thoughts. Next time you see a person with obesity - whether across the street or in the mirror - remember that obesity is a devastating, lifelong, metabolic disorder caused by a worldwide, multi-generational food science experiment gone horribly wrong.

Keep in mind that none of us knows where someone else with obesity may be on their journey. The person you see who currently weighs 275 pounds may have weighed 325 pounds last year. The person you see may have the wrong information, tried many times to lose weight, and decided to take a break or even give up. The person you see may have all the right information but decided it's too much work to fight obesity or chooses not to prioritize their weight or health at this time for whatever reason - that's their prerogative - it's their body.

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.