12:17 GMT19 January 2021
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    The largest-ever study has found that, while exercise and diet are important, genes play a major role in obesity, weight gain and where fat is storied in the body, meaning that some people may just be born to be fat.

    Scientists investigated the genetic basis of body mass index (BMI), a common measure of overall obesity. The GIANT (Genetic Investigation of Anthropometric Traits) project, identified over 100 locations across the genome that play a role in obesity. The study reinforces the role genetics play in obesity and its links to diabetes and heart disease.

    By analysing genetic samples for over half a million individuals as part of the GIANT research project, researchers found more than 100 locations across the genome that play roles in various obesity traits. Learning more about the genes and biological processes may guide the development of weight-loss therapies, and help doctors tailor the health advice they give to patients.

    “Our work clearly shows that predisposition to obesity and increased body mass index is not due to a single gene or genetic change,” says senior study author Elizabeth Speliotes, assistant professor of internal medicine and computational medicine and bioinformatics at the University of Michigan Health System.

    “The large number of genes makes it less likely that one solution to beat obesity will work for everyone and opens the door to possible ways we could use genetic clues to help defeat obesity."

    “Presently we have no way of knowing if obese individuals will develop these obesity-related metabolic diseases and if so which ones,” says Speliotes, who is also a gastroenterologist at the U-M Health System.  “We envision using these genetic markers to help doctors decide which treatments would work best to keep patients healthy.”

    Unhealthy to Be Belly, Belly Fat

    People with waistlines larger than hip circumferences have more belly fat surrounding their abdominal organs. In a companion study, an analysis of 224,459 individuals helped identify 49 sites in the genome associated with waist-to-hip ratio — a measure of body fat distribution.

    Accumulation of fat, especially around the stomach, increases the risk of cardiovascular and metabolic diseases. 

    Some sites display stronger effects in women than men, demonstrating that genetic regulation of body fat distribution varies between the sexes.

    “We need to know these genetic locations because different fat depots pose different health risks,” says Karen Mohlke, Ph.D., professor of genetics at the University of North Carolina School of Medicine and a senior author on the paper that examined waist-to-hip ratio of fat distribution.

    “If we can figure out which genes influence where fat is deposited, it could help us understand the biology that leads to various health conditions, such as insulin resistance/diabetes, metabolic syndrome, and heart disease.”

    Tags:
    obesity, health
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