About a quarter of adults in the UK are living with obesity - but scientists have found it is not just lifestyle that affects the likelihood of putting on weight.
While cutting down on fatty foods and exercising can help prevent obesity, researchers have also identified more than a dozen genes that increase a person's risk of developing the condition, including five new ones.
The global epidemic of obesity increases the risk of developing health conditions such as Type 2 diabetes, heart disease and osteoarthritis.
The study, published in the journal Nature Communications by researchers at Penn State, involved 850,000 adults with ancestries across six continents and found 13 genes associated with obesity. While eight of these genes had been found in previous studies, five were identified for the first time after having no previous links to obesity.
Researchers said their findings could help develop medicine by revealing the key genes from around the globe that might be missed in single-population studies.
Santhosh Girirajan, professor of genomics and head of the department of biochemistry and molecular biology in the Penn State Eberly College of Science, said: “Obesity is a complex trait that is influenced by many genetic and lifestyle factors.
“Some of the previously discovered obesity genes appear to only have a significant association to obesity in Europeans, which could limit their potential as therapeutic targets for a global population.
“Our cross-ancestry approach is helping us develop a more comprehensive view of the factors involved in obesity, which will hopefully help us develop effective therapies that can be applied through precision medicine.”
Researchers used data from more than 450,000 adults in the UK Biobank, a database of UK health data, and almost 385,000 adults in the All of Us Research Program, a US National Institutes of Health precision-medicine initiative with a more inclusive cohort that mirrors US ancestral diversity.
Ancestries from Africa, America, East Asia, Europe, the Middle East and South Asia were included in the study.
They found 13 genes with statistically significant association to BMI in the European group that were replicated in the non-Europeans.
Of these, eight had been previously associated with obesity, including MC4R and BSN. Five genes - YLPM1, RIF1, GIGYF1, SLC5A3 and GRM7 - had not been associated with obesity in previous studies.
The researchers found that these novel genes had about a three-fold increase in risk of severe obesity, a level of impact similar to MC4R and BSN.
Like genes previously associated with obesity, the newly identified genes are found in the brain and adipose tissue, known as fat, and were linked to obesity traits such as increased body fat percentage.
The researchers also found that several of these genes contribute to other obesity-related conditions, including Type 2 diabetes, hypertension and heart disease.
Some of the biobank data included plasma proteomics data - a comprehensive list of proteins found in blood plasma. This enabled researchers to identify changes in circulating proteins linked to the obesity genes they identified.
These changes point to potential drug targets and biomarkers that could guide future treatments, the researchers said.
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