Could it be possible to prevent our brains from responding so strongly to the sight of tantalising treats? Catherine De Lange from New Scientist finds out.
It's a familiar feeling. After a large meal you feel full, but a glimpse of a slice of gooey, rich chocolate cake is enough to get you salivating again.
Could it be possible to prevent our brains from responding so strongly to the sight of tantalising treats? The answer is yes, according to new research which suggests that some anti-obesity drugs work by dulling this brain response to the sight of appetising, high-calorie food.
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Paul Fletcher from the University of Cambridge and colleagues wanted to understand how drugs that help people lose weight affect the brain. To find out, they gave 24 obese people either the anti-obesity drug Sibutramine or a placebo for two weeks and then scanned their brains while showing them pictures of high- or low-calorie foods, such as chocolate cake or broccoli.
Not only did volunteers taking the drug eat less and lose weight during the two weeks of the study, their hypothalamus and amygdala – areas of the brain involved in reward – also responded more weakly to the sight of high-calorie foods than those given the placebo.
"This is the first evidence that an anti-obesity drug changes brain function," says Ed Bullmore, who is also at the University of Cambridge and also worked on the study. More importantly, says Bullmore, it shows how these brain changes are correlated with a change in eating behaviour, and ultimately weight loss.
Hooked on fat
In the same way that some people respond more strongly than others to addictive drugs, the study could help explain why some seem more prone to obesity than others, says Bullmore. "You might imagine that some people that are obese are predisposed by their brain circuitry to experience stronger rewards when they eat these highly fatty foods."
Sponsored by pharmaceutical company GlaxoSmithKline (which does not manufacture Sibutramine), the research also shows how useful brain scans might be in testing the potential of new anti-obesity drugs before going to large-scale clinical trials.
Previous research has shown that reward pathways in the brain become less active as people gain weight, causing them to eat more. Longer studies will be needed to determine whether the brain changes seen in this study will persist or adapt to the drug over time.
