It's in the Genes: Study Discovers 79 Forms of Genetic Obesity, More Than Previously Thought

A new study led by researchers from McMaster University has shown that obesity comes in numerous forms, and most of them are linked to people's genes.

The study, published in the journal Obesity Reviews, noted that the researchers analyzed 161 papers plus two independent review of each paper and found 79 obesity syndromes reported in the studies. Previously, only 20 to 30 genetic conditions that can cause obesity have been thought to exist.

Live Science said an example of genetic obesity syndrome is a condition called Prader-Willi syndrome, which is associated with excessive hunger and abnormally large food intake that could make a person obese.

"The reason we studied this is very simple," David Meyre, senior author of the study published in Obesity Reviews told CNN. "Every time I was writing a research paper and I was describing what we knew about the genetics of obesity, I didn't have a reference."

"For the study, we focused on monogenic forms of obesity," said Meyre who explained that monogenic or "Mendelian" forms mean that you develop the disease once there is a single mutation.

"It's not that it increases your risk, it's 100% sure you develop the disease," he said.

According to the study, of the catalogued 79 syndromes, 43 have never been assigned a name while 22 are completely unknown to scientists, meaning they know nothing about the gene or the chromosome associated with them. Other syndromes involve intellectual disabilities and facial abnormalities.

The study highlights the commonness of faulty biological mechanism accountable for the onset of obesity.

Meyre said although genetic forms of obesity are relatively rare in the population, as in "one in a million" births, it is important to understand the genetics of obesity to better treat the disease, which is one of the most universal, chronic diseases in need of new strategies for medical treatment.

The World Health Organization data shows worldwide obesity has more than doubled since 1980 -- over 600 million adults were obese in 2014 while 41 million children under the age of five were overweight or obese.