New Insights into the Biology of Obesity

Obesity is related to how much we eat and to how we store energy. Two reports reveal new information about both phenomena.

When we eat, the pleasure we feel correlates with the release of dopamine in the dorsal striatum of the brain. Functional magnetic resonance imaging (MRI) of the brain was recorded in 76 subjects who drank chocolate milkshakes and tasteless solutions. When only the chocolate-shake results were considered, obese subjects exhibited lower dopamine release in the dorsal striatum than did nonobese subjects. A particular polymorphism in the gene for the dopamine D₂ receptor correlated with reduced dopamine release. The investigators concluded that obese individuals could have a genetically based deficiency in the pleasure they…