Childhood obesity has reached epidemic proportions in the United States and is rapidly increasing among industrialized nations. According to the U.S. Centers for Disease Control and Prevention, obesity rates have more than doubled in children and quadrupled in adolescents in the past 30 years. Obesity affects 17% of children and teens nationwide, and in 2012 alone more than one-third of children and adolescents were classified as overweight or obese. Moreover, obesity is associated with an estimated $14.1 billion in additional prescription drug, emergency room visit, and outpatient visit costs each year, according to the Endocrine Society's Facts and Figures Report.
Now, a new study led by researchers at Yale University has found a connection between gut microbiota and fat distribution in children and teenagers. The investigators found that children and adolescents who were obese had different microorganisms living in their digestive tract than their lean counterparts.
“Our findings show children and teenagers with obesity have a different composition of gut flora than lean youth,” explained senior study investigator Nicola Santoro, M.D., Ph.D., associate research scientist in the department of pediatrics at Yale University. “This suggests that targeted modifications to the specific species composing the human microbiota could be developed and could help to prevent or treat early-onset obesity in the future.”
The findings from this study were published recently in the Journal of Clinical Endocrinology & Metabolism in an article entitled “Role of Gut Microbiota and Short Chain Fatty Acids in Modulating Energy Harvest and Fat Partitioning in Youth.”
The Yale team managed to examine the gut microbiota and weight in 84 children and teenagers who were between 7 and 20 years old. The participants included 27 youth who were obese, 35 who were severely obese, 7 who were overweight, and 15 who were healthy weight. Researchers analyzed the participants' gut microbiota. The participants underwent magnetic resonance imaging (MRI) to measure body fat partitioning, provided blood samples, and kept a 3-day food diary.
The researchers discovered eight groups of gut microbes that were linked to the amount of fat in the body. Four of the microbial communities tended to flourish in children and teens with obesity compared to their normal-weight counterparts. Additionally, smaller amounts of the other four microbial groups were found in participants who were obese compared to children and teenagers of normal weight. The gut microbiota found in youth who were obese tended to be more efficient at digesting carbohydrates than the gut flora of teenagers and children of normal weight. “A significant association was found between the Firmicutes to Bacteroidetes ratio, and the abundance of Bacteroidetes and Actinobacteria with body mass index, visceral and subcutaneous (SC) fat,” the authors wrote. “Plasma acetate, propionate, and butyrate were associated with body mass index and visceral and SC fat and with hepatic de novo lipogenesis. Moreover, the rate of carbohydrate fermentation from the gut flora was higher in obese than in lean subjects.”
Also, the children with obesity tended to have higher levels of short-chain fatty acids in the blood than children of normal weight. The study found short-chain fatty acids, which are produced by some types of gut bacteria, are associated with the production of fat in the liver.
“Our research suggests that short-chain fatty acids can be converted to fat within the liver and then accumulate in the fat tissue,” Dr. Santoro remarked. “This association could signal that children with certain gut bacteria face a long-term risk of developing obesity.”