Science Update - Bad Diet Food and the Placebo effect

Bob - This week for The Naked Scientists I'm going to talk about why diet foods might actually make kids fat. But first, Susanne's going to tell us why the placebo effect works on some people and not others.

Susanne - Some patients get powerful pain relief from a sugar pill if they're told it's real medicine. It's called the placebo effect, and scientists have long puzzled over what causes it, and why it helps some people more than others. Now University of Michigan neuroscientist Jon-Kar Zubieta and his colleagues have found that people who get the most pain relief from placebos also show increased activity in a tiny region of the brain called the nucleus accumbens.

Jon-Kar Zubieta (University of Michigan): So, basically, what this was telling us is that placebo activates dopamine and the magnitude of activation in this particular brain region predicted how well the placebo was going to work in these individuals.

Susanne - Zubieta doesn't know why some people have more dopamine activity in the nucleus accumbens, and therefore respond better to placebos, but he thinks genetics may play a role.

Bob - Thanks, Susanne. A new study suggests that popular diet foods could actually cause children to overeat and gain weight. A team of researchers at the University of Alberta found that when they fed juvenile rats low calorie foods that taste just like higher calorie versions, the rats began to overeat their normal diet. Sociologist David Pierce explains.

David Pierce (University of Alberta): In the young juvenile rat, their bodily system is in some sense fooled by the taste cue, such that the body thinks that it hasn't had any calories, so they ate more at their regular meal.

Bob - Pierce says that rats and humans have a similar response to taste conditioning, so children might be prone to overeat if exposed to diet foods when they're young. Instead, he suggests offering kids healthful, nutritious meals and leaving the low-calorie options on supermarket shelves.

Susanne - Thanks, Bob. Next time, we'll tell you about a computer with a sense of humour. Until then, I'm Susanne Bard...

Bob - ...and I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists...