Print Edition: October 2, 2013
The connection between overeating and the brain has long been established. An area of the brain known as the lateral hypothalamus has often been labelled the “eating center” because stimulation of the region caused rats to overeat, even when apparently satiated with food.
However, while it is obvious to scientists that there is a connection between the lateral hypothalamus and over-consumption, the title of “eating centre” has been hotly debated. It has been pointed out that this area has more to do with stimulating behaviour in general, such as wheel-running in rats, not just overeating.
As for its sister “satiety center” (in the ventromedial hypothalamus), lesions to this area, while causing rats to overeat, only caused them to do so if the food was tasty. So while the general cortical area was known, the precise mechanisms behind overeating in particular remained unknown.
Now a new study from the University of North Carolina has pinpointed the actual neural circuitry behind this phenomenon. Research conducted by J.H. Jennings, G. Rizzi, A.M. Stamatakis, R.L. Ung, and G.D. Stuber focused on the gaba neurons found in the bed nucleus of the stria terminalis (BNST), a structure that connects the amygdala and the lateral hypothalamus.
The gaba neurons were stimulated in the brains of mice, and upon stimulation the mice began to overeat, particularly preferring high-fat food. It is believed this stimulation also caused reward behaviour, indicating that the mice were feeling pleasure by eating.
“They would essentially eat up to half their daily caloric intake in about 20 minutes,” said Stuber in Science Daily. “This suggests that this BNST pathway could play a role in food consumption and pathological conditions such as binge eating.”
“The study underscores that obesity and other eating disorders have a neurological basis. With further study, we could figure out how to regulate the activity of cells in a specific region of the brain and develop treatments.”
You, Me, and UFV
Eating disorders are widely misunderstood despite their prevalence. The American Psychiatric Association work group on eating disorders estimates that some eight per cent of women suffer from either anorexia nervosa or bulimia nervosa, and in 2001 the Canadian Paediatric Society reaffirmed that eating disorders were the third most chronic illness in teenaged girls.
While eating disorders are not limited to women, it is a well-documented fact that female sufferers far outnumber the male. Now biological studies are confirming this finding. Earlier this year, it was discovered by Michigan State University (MSU) that female rats were far more susceptible to binge eating than male rats – in fact, four to 10 times more likely. One possibility, which MSU is currently exploring, is whether or not women are more affected by rewarding stimuli, such as high-fat and sugary foods.
“Most theories of why eating disorders are so much more prevalent in females than males focus on the increased cultural and psychological pressure that girls and women face,” said MSU lead study author Kelly Klump in Science Daily. “But this study suggests that biological factors likely contribute as well, since female rats do not experience the psychosocial pressures that humans do, such as pressures to be thin.”
Psychologists have long known that eating disorders are not a simple matter of willpower or self-control, but now the biology is firmly in place to prove it once and for all, hopefully displacing the current shame and stigma surrounding the issue. Finally, more effective treatments can be developed for a mental disorder notorious for having the highest rate of mortality.