Non-Alcoholic Fatty Liver Disease: Consequences of Childhood Overweight & Obesity
By Sarah Lewis
The long term effects of childhood overweight and obesity include such well known diseases as Type 2 diabetes and cardiovascular disease. Another chronic condition associated with excess body weight on the rise in both children and adults is Non-Alcoholic Fatty Liver Disease (NAFLD), a spectrum of diseases characterized by excess fat deposition in the liver. There is currently no medical treatment for the condition, making weight loss the only option for improvement. Untreated NAFLD may progress to an inflamed and eventually poorly functioning liver, including cirrhosis and liver cancer. One study estimates that the advanced form of NAFLD, known as NASH or Non-Alcoholic Steatohepatitis, is expected to be the leading cause of liver transplants by 2020; in 2001 it accounted for only one percent of them.
Among children and adolescents, NAFLD prevalence has increased more quickly than overweight and obesity prevalence. While excess weight is not the only cause of NAFLD, the American Liver Foundation reports that in the United States about 10 percent of all children and 38% of obese children have NAFLD, placing it squarely at the intersection of endocrinology and pediatrics. As shown in the graph below, the Centers for Disease Control and Prevention estimate that childhood obesity has more than doubled in children and quadrupled in adolescents in the past three decades.
Understandably, teenagers have a higher prevalence of NAFLD than younger children and adolescent prevalence has more than doubled in the past two decades. Overall, 12 percent of high school students in Michigan are estimated to be obese and another 14 percent are overweight. Youth Risk Behavior Survey data compiled by the MOTION Coalition (see http://dwcha.org/michigan-organizations-to-impact-obesity-and-nutrition-coalition.html) show that middle and high school students in the southeastern Michigan counties of Macomb, Washtenaw and Wayne have higher rates of overweight and obesity than the state average. For example, 17% of Wayne County high school students are overweight and 14% are obese.
Dr. Stacy Leatherwood, pediatrician at Henry Ford Health System and Physician Champion for Childhood Wellness at LiveWell (see http://www.henryfordlivewell.com/letsgethealthy), explains that a large segment of kids are at risk because of diets high in saturated fats and sugars that lead to obesity. Once children and adolescents hit the overweight mark, “you start seeing changes in the liver at the cellular level.”
Besides excess weight, male sex and Hispanic race/ethnicity can increase risk for NAFLD, even after adjusting for factors such as age, income, education, body mass index and diabetes status. Dr. Leatherwood confirmed that Hispanic children, especially boys, register an especially high rate of NAFLD. Importantly, some Hispanics have a genetic predisposition to store excess fat in the liver due to overproduction of triglycerides. Furthermore, 17 percent of children and adolescents are obese, but Hispanic and black youths are significantly more likely to be obese than others (22.4 percent and 20.2 percent, respectively versus 14.1 percent).
Being diagnosed with NAFLD and related conditions such as Type 2 diabetes at a young age means “these children will live with this illness for a lifetime, and are more likely to experience the associated complications,” says Dr. Leatherwood. The good news is that NAFLD presents not just a challenge but an opportunity to intervene at multiple points. The only known way to reduce fat in the liver is gradual weight loss through eating healthier and increasing physical activity, so NAFLD implies a multisectoral approach in which communities, schools and health care systems can all play a role.
In her experience, Dr. Leatherwood considers at least three points of intervention: the doctor-patient relationship, school-based programs, and community-based programs and policies such as nutrition labeling to make healthier choices. Tools such as “5-2-1-0” allow people to start small by incorporating tangible behavior changes that lead to healthy lifestyles. Effective behavior change can happen when people are targeted and then supported “in as many different areas of their life as possible.”
American Liver Foundation: “Pediatric Non-Alcoholic Fatty Liver Disease”http://www.liverfoundation.org/chapters/rockymountain/doctorsnotes/pediatricnafld
CDC: “Childhood Obesity Facts”http://www.cdc.gov/healthyyouth/obesity/facts.htm
2009 Michigan Youth Risk Behavior Survey https://mdoe.state.mi.us/schoolhealthsurveys/ExternalReports/CountyReportGeneration.aspx
New York Times: “Threat Grows From Liver Illness Tied to Obesity” http://well.blogs.nytimes.com/2014/06/13/threat-grows-from-liver-illness-tied-to-obesity/?_php=true&_type=blogs&_php=true&_type=blogs&_php=true&_type=blogs&_r=2&
Sarah Lewis is the Kellogg Population Health Fellow at the Detroit Wayne County Health Authority