As Americans grapple with ever-increasing waistlines, science is looking at the biology behind the compulsion to eat. What exactly makes some people weigh 350 pounds and others 150? Researchers have discovered a chemical in your brain proven to regulate body weight, but can pinpointing a "fat gene" signal the road to a remedy? Learn the latest in weight research in this NOVA scienceNOW video. Turkish subtitles will be added soon. No copyright intended, all the copyrights belong to PBS NOVA. www.pbs.org/wgbh/nova/sciencenow/ Support PBS! www.shoppbs.org/family/index.jsp?categoryId=11580318&ab=NOVAscienceNOW Or donate: www.pbs.org/about/support-our-mission/