If the rate of obesity and overweight continues to rise, 75 percent of adults and nearly 24 percent of US children and adolescents will be overweight or obese, recent studies suggest. Obesity is an increasingly alarming problem worldwide that rivals smoking as a cause of illness and premature birth, but efforts are done in order to better understand the factors that contribute to this health condition.

Following this line, a new study examines the pathways that contribute to obesity. The National Institutes of Health Study, that appears in the August 28 New England Journal of Medicine, shows that a brain chemical, known as BDNF (brain derived neurotrophic factor), plays a role in regulating the quantity of food that people eat and their chances of becoming obese.

The NIH study involved 33 children and adults with WAGR syndrome, which is a rare genetic condition in which individuals lack some groups of genes. The symptoms of WAGR syndrome include Wilms tumor, a tumor of the kidney, aniridia, genitourinary anomalies, and mental retardation. Obesity was observed in a subgroup of WAGR syndrome patients. The genetic aberration occurs in one out of every 500,000 to 1 million persons. Half of the group studied lacked one or two genes for the brain chemical called BDNF.

The scientists studied the relationship between genotype and body-mass index (BMI) and found that every person of the first group was obese by age 10 and reported high levels of overeating compared to the general population. The 14 other patients who had two working copies of the BDNF gene were no more likely to develop childhood onset obesity than the general population. They were less tempted to overeat.

“We suspect that BDNF has important issues in many parts of the brain, including memory and ability to sense pain,” said the study’s first author, Jack Yanovski, head of the Unit on Growth and Obesity at NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. He said that a larger segment of the population may have the same problem. The fact that some people can’t control their eating habits or lose weight may be attributed to gene deletions.

To conclude, the findings add another factor on the list of factors that predispose children and adults to obesity. The senior author of the study, Jack A. Yanovski, M.D., Ph.D., of NICHD’s Unit on Growth and Obesity, said that the brain chemical is believed to work in a combination with other substances, including the hormone leptin, that regulate appetite and body weight. It appears that leptine indirectly triggers the release of BDNF in the hypothalamus, the part of the brain which plays a role in controlling eating.

Researchers said that BDNF is “just a small part of the puzzle” and more research needs to be done in order to develop new drugs to treat obesity in people who don’t make enough BDNF.

Obesity is one of the main health problems is the world, with 400 million obese people classified by the World Health Organisation around the world. Obesity is also a significant risk factor for a number of chronic diseases such as heart disease and type 2 dyabetes.