If I were to tell you that some of my favorite things to do would be to ride my mountain bike constantly, rock climb, go white water rafting and cruise the slopes on a pair of skis you could probably hazard a guess as to where I am from. Living in Colorado for most of my life has given me access to a large playground of mountains in which to partake in numerous activities. I am fortunate none the less to live in one of the fittest states in the nation. According to Calorielab, Colorado is considered the slimmest state in the United States. If we look at our country on a whole, we see that we are one of the most obese countries in the world. According to USA today, out of 33 countries with advanced economics, the United States is the fattest nation. All other factors aside the US ranks 3rd in the world just under a few small pacific islands. The interesting thing is that anywhere between 16 and 33% of children and adolescents are obese.
Obesity is the result of unhealthy eating habits, genetic influences, biological influences and even cultural factors. For years scientists have studied obesity in an attempt to help lower the amount of deaths each year and improve their overall quality of life. Recent studies suggest that there may be a neurological component to obesity.
Thaddeus Unger and colleges were testing both mice with normal levels of BDNF and also mice with BDNF receptors blocked. What they found is that by using viral mediated selective knockdown of BDNF in the ventromedial hypothalamus and also the dorsomedial hypothalamus they were able to see BDNFs role in energy balance regulation. These mutants more specifically exhibited hyperphagic behavior and obesity as a result. This exhibited obesity is most likely the result of an upset in the regulated equilibrium between caloric intake and expenditure. So BDNF, contrary to its role as a plasticity factor and neuronal growth tool, is now being seen as a key player in the neural circuits of energy homeostasis.
This is particularly interesting when thinking about child obesity. Since BDNF spurs on neuronal development during childhood, a good assumption would be that it would stunt development and thus growth. In fact the opposite happens. When there was depletion of BDNF or its receptor TrkB during the early-postnatal stage of development, mice grew up to exhibit aggressive behaviors as well as dramatic obesity.
BDNF has even been linked to the intake of food in mice. Reports by Unger suggest that signaling through the BDNF/TrkB pathway promote satiety in the adult animal. So infusion or an overexpression of BDNF into the brain of mature mice significantly reduce food intake. The reverse is also true. In times of fasting in which food is withheld from the mice, there is a decrease in the amount of BDNF mRNA in the VMH. The amount of food intake plays a role in obesity because indulgence or overeating is often a symptom of many obese people.
So when considering a place to raise a family, I would stay away from Mississippi or Texas, but the importance of BDNF promoting satiety and also regulating energy homeostasis may be something else to consider. Can neuroscience help the heavy set? Science seems to think so. Further research may prove to more specifically target the circuitry involved and help those who suffer from obesity.
Thaddeus J. Unger, German A. Calderon, Leila C. Bradley, Miguel Sena-Esteves, and Maribel Rios. Ô??Selective Deletion of Bdnf in the Ventromedial and Dorsomedial Hypothalamus of Adult Mice Results in Hyperphagic Behavior and ObesityÔ?? The Journal of Neuroscience, 26 December 2007, 27(52):14265-14274