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The scientists were interested in the activation of the striatum, an area rich in dopamine neurons and involved in the processing of hedonic rewards. (When your striatum is excited, life is good.) Sure enough, obese people tended to have reduced activation in the striatum after sipping the ice cream treat, which led to increased consumption. In other words, they kept on consuming the milkshake in a manic search for satisfaction.

A second study found that, over time, people with a polymorphism that leads to reduced dopamine receptors in the striatum also tended to put on weight, suggesting that obesity is, at least in part, triggered by a shortage of neural pleasure. Of course, this contradicts the popular (and deeply unfair) cultural stereotype of obesity, which assumes that people who are overweight are gluttons, unable to resist temptation. In fact, they are the opposite of gluttons: The reason they eat too much is because they don’t enjoy their food enough. They keep on sipping the milkshake precisely because it isn’t pleasurable.

Maybe this is why Americans need ever larger portion sizes: Because we didn’t make the milkshake ourselves, because that dinner only required a few minutes of work, we need to consume more calories to get the same baseline of satisfaction.

Why Making Dinner Is a Good Idea | Wired Science | Wired.com (via slantback)