Over 600 million adults around the world are obese, while another 1.3 billion are considered overweight. This epidemic has led to hundreds of thousands of deaths each year, along with over $147 billion in obesity-related medical costs in the United States alone. Decreased physical activity and subpar diet are certainly part of the reason, but that might not be the entire story. Two new papers published in Nature describe two large genome-wide studies that strengthen the genetic basis for a person's predisposition to obesity, and also where fat is stored on the body. It is hoped that this will help predict not only an individual's risk for obesity, but also many of the comorbidities associated with it, and even possibly permit the development of future treatments.
The first paper (Locke, et al.) compared the genomes and body mass index (BMI) scores of over 339,000 individuals. This revealed 97 loci in the genome that appear to be connected with obesity; roughly 60 of which were previously unknown. Additionally, the regions that relate to a person's predisposition for obesity are also connected to the central nervous system that has to do with eating.
“Our work clearly shows that predisposition to obesity and increased body mass index is not due to a single gene or genetic change,” senior author Elizabeth Speliotes said in a press release. “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.”
The large number of genes involved adds complexity to the obesity problem, as it makes one-size-fits-all treatments unlikely. On the other hand, it does allow the opportunity to use these various loci to determine which genes are involved with the onset of different comorbid conditions. Nailing down the respective mechanisms could possibly lead to a number of new treatments.
“Presently we have no way of knowing if obese individuals will develop these obesity-related metabolic diseases and if so which ones,” Speliotes continued. “We envision using these genetic markers to help doctors decide which treatments would work best to keep patients healthy.”
In the second paper (Shungin, et al.), the waist-to-hip ratio of over 224,000 people were compared to their genomes in order to determine a possible genetic component to where fat is distributed on the body. Indeed, the researchers found 49 regions that corresponded to dispersal of body fat.
“We need to know these genetic locations because different fat depots pose different health risks,” the paper’s senior author Karen Mohlke explained. “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.”
Though there is a genetic component, that alone does not account for the fact that global obesity rates have doubled within the last 35 years. Obesity is linked to a number of diseases including hypertension, type 2 diabetes, psychological disorders, various respiratory diseases, decreased fertility, and even certain types of cancer. There will be no quick and easy fix to reversing this trend, but perhaps confirming the genetic link will help assuage some of the stereotypes about obese individuals, allowing them to pursue proper treatment.