Researchers have found a ‘clear genetic trigger for obesity’ that applies to some people

Obesity isn’t just a matter of food and exercise — it may be in your genetic code, according to new research.

“Obesity’s causes are very complex and in the majority of cases, the combination of many factors. In this study, however, we found a clear genetic trigger for obesity,” said lead study author Dr. Mattia Frontini, British Heart Foundation senior fellow and an associate professor in cellular biology at the University of Exeter in the United Kingdom, in an email.

Researchers used data from the UK Biobank, a large biomedical database and research resource that follows people long term, according to the study published Thursday in the journal Med. They compared data from people with two faulty copies of a particular gene (SMIM1) and those who did not have the two faulty copies.

Women with the gene mutation weighed an extra 4.6 kilograms (10.14 pounds), and men with the variant weighed an extra 2.4 kilograms (5.29 pounds), according to the study.

The faulty copies of the SMIM1 gene cause decreased function in the thyroid and declining energy expenditure, Frontini said, “which means that given the same food intake, less energy is used and this excess is stored as fat.”

Not only is the correlation significant, but this study also identifies a specific gene mutation, which isn’t always the case in research, said Dr. Philipp Scherer, director of the Touchstone Diabetes Center at the University of Texas Southwestern Medical Center. He was not involved in the study.

“It is an exciting study in that it puts a new gene on the map,” Scherer said. “It’s an actual gene, rather than just a genomic locus with a mutation somewhere where we don’t understand. … We think we’re looking at a gene here that we can further study.”

This genetic finding is ‘pretty rare’

This particular genetic finding doesn’t apply to a large population of people with obesity — only about 1 in 5,000 people have this genetic makeup, Frontini said.

“That’s pretty rare, but you multiply that to a population of 10 (million), 15 million and there’s quite a few people out there that would walk around with that mutation and maybe weren’t fully aware of the fact that there is a genetic explanation for their struggle with obesity,” Scherer said.

Dysfunction in the thyroid is common, affecting almost 2% of the population in the UK, Frontini said. And thyroid dysfunction is treated regularly with a relatively inexpensive medication, Frontini said.

The next step in the research is to find out if people with the SMIM1 mutation qualify to treat their thyroid with medication, he added.

“If they do, we plan to run a randomized clinical trial to determine if they would benefit from the treatment,” Frontini said. “The hope is that they will, and we can improve their quality of life using a cheap, safe treatment.”

The best approach in the meantime

Weight isn’t just a matter of willpower or laziness. The size and shape of your body is determined by many factors — some of which you have control over and others you don’t, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Among these factors are lifestyle habits, the amount of sleep you get, medications, health problems, where you live and work, and genetics, according to the institute.

Research into genetic factors and potential treatments is still underway, but Scherer said the current best approach to medical treatment of obesity is GLP-1 medications.

Severe restrictive dieting is not the answer, Brooke Alpert, a registered dietitian and author of “The Diet Detox: Why Your Diet Is Making You Fat and What to Do About It,” said in an earlier CNN article.

Demonizing foods too much may make you crave them more, and then the guilt you feel when you give in can lead to a cycle of fluctuating between restricting yourself and bingeing, she added.

If you want to make changes to your lifestyle, it’s best to try a gradual, sustainable approach while maintaining a healthy relationship with food, Emily Feig, a postdoctoral fellow at Massachusetts General Hospital, said in the same CNN report.

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