Pioneer findings on obesity relate this condition to a decrease in function of reward pathways that operate in the brain.
This research sponsored by GlaxoSmithKline implicates that new anti-obesity drugs can be tested for brain function before starting large scale clinical trials. Further research is required to ascertain if the brain changes persist or adapt with time.
Brain pathways are already known to be less responsive in subjects that gained weight over a fixed period as revealed from MRI scans. Subjects derive the normal sensation of pleasure by consuming larger quantities of food. This creates a vicious circle of further reduction in reward response.
Reward pathway functions when we tend to eat with a full stomach after a square meal. The craving is associated with sight of foods we relish. This study reveals that one of the side-effects of anti-obesity drugs is preventing the brain response to the sight of appetizing, high-calorie food.
Paul Fletcher and his colleagues from the University of Cambridge administered anti-obesity drug Sibutramine and a placebo for a period of 2 weeks on 24 obese people. Patients were then showed pictures of chocolate cake and broccoli as their brains were scanned. Sibutramine treated patients lost weight and ate lesser compared to control set.
Also MRI imaging of hypothalamus and amygdala, two regions of brain involved in reward response showed a weak response to sight of chocolate cake. Chocolate cake was the high calorie food and broccoli the low calorie food in this study.
This research is significant because it correlates brain activity to eating behavior and weight loss. "This is the first evidence that an anti-obesity drug changes brain function," says Ed Bullmore, one of research scientists. He draws parallels between responses of some people over others to addictive drugs to propensity of only some people towards obesity.
Reward response is stronger in obese people when they eat highly fatty foods largely because of modifications in their brain.