Two studies zero in on DNA-based drivers of weight. Is obesity written in our genes? In two separate papers, published in the journal Science and in the Journal of Clinical Investigation (JCI), researchers describe new genetic factors that could explain weight gain in some people. In the Science study, researchers at Boston Children’s Hospital studying mice found a rare genetic mutation that prevented the animals from burning off fat calories. They also found the same gene was mutated in a group of obese people. And a team based at University College London reported in JCI that a specific form of a gene previously linked to obesity, FTO, can increase craving for high-fat foods. The discoveries add to the growing body of knowledge about the biology behind weight, and the results confirm that while it’s represented by a single number, weight is the complex combination of a multitude of different metabolic processes, from brain systems that regulate appetite to enzymes that control how efficiently calories are turned from food into energy that the body needs. Making matters even more confusing, these factors are also likely influenced by environmental contributors such as diet and lifestyle. In the mouse study, the research team determined that mutations in the Mrap2 gene led the animals to eat less initially but still gain about twice as much weight as they normally would. While their appetites returned, these mice continued to gain weight despite being fed the same number of calories as a group of control animals. That led the scientists to figure out that the mice with the mutated gene were simply sequestering fat rather than breaking it down for energy. The mice, like people, possessed two copies of the gene, and mice with even one defective copy experienced significant weight gain, although not as much as those who had two mutated versions of Mrap2. The scientists found a similar pattern among a group of 500 obese people; they detected four mutations in the human version of Mrap2, and each of the obese individuals possessed only one … Continue reading New Genes IDd in Obesity: How Much of Weight is Genetic?