Obese people who say 'It's my genes' may be telling the truth after scientists discovered 80 different genetic conditions suffered by the massively overweight.
Researchers have shown that, while relatively rare in the general population, there are a large number of varied, genetic syndromes associated with obesity.
Investigators from McMaster and the University of British Columbia have catalogued 79 syndromes with obesity that have been described in the literature - well up on the 20 to 30 that were thought to exist.
The research was published today in Obesity Reviews and led by David Meyre, an associate professor of the Department of Health Research Methods, Evidence, and Impact with the Michael G. DeGroote School of Medicine.
Dr Meyre said: "Rare genetic forms of obesity with many additional clinical features, such as intellectual disability, facial and organ-specific abnormalities, do exist."
Yuvreet Kaur, the study's first author, added: "These syndromes, although individually rare, are much more numerous and diverse than anticipated."
Serious health issue
Obesity is a serious health issue, and rates have risen dramatically over the past three decades.
Complications associated with obesity include an increased risk of Type 2 diabetes, mental health issues, osteoarthritis, gallbladder disease, hypertension, fatty liver, coronary heart disease, and certain forms of cancer.
In their search of seven databases and analysis of 161 papers, Dr Meyre and his colleagues found that 79 obesity syndromes have been previously reported.
Of the 79 syndromes, 19 have been genetically solved, to the point where a lab test could confirm a doctor's suspicions.
Another 11 have been partially clarified, and 27 have been mapped to a chromosomal region.
For the remaining 22 syndromes, neither the genes nor the chromosomal locations have yet been identified.
Dr Meyre added national and international collaborations are needed to identify the genes responsible for these syndromes considering they are very rare, and that "this paper is a critical step to boost the clinical and genetic research on this topic."
He added: "A more clear understanding of the genetic causes of these syndromes may not only improve the lives of those afflicted with these mutations, but will also help us understand the genes and molecules that are important in obesity among members of the general population."