Why Fat People Tend to Eat More

A psychology researcher at the University of Texas has proposed an interesting mechanism in which obese people are made to eat more than normal weight people. It’s been published in the journal Science. It goes like this:

When someone eats, their brain’s reward center responds by releasing the substance dopamine. This release of dopamine is considered pleasurable. Compared with the brains of lean people, an obese person’s brain is less active in releasing dopamine. So the obese individual has to take in more of the rewarding substance – such as food or drugs – to experience the same level of pleasure as other people.

The obese person’s decreased activity with respect to dopamine release is related to a gene (Taq1A1) that’s associated with a reduced number of dopamine receptors. Using fMRI, the researchers determined the activity of the specific part of the brain responsible for dopamine release – the striatum – in 76 female volunteers while they drank a chocolate milkshake, and followed their weight over the next 12 months. Those whose striata were less active, and who also possessed the TaqlA1 gene, were more likely to put on weight during the next 12 months.

It’s not unlike drug addiction. The heroin addict can start with low doses of the drug, but develops a blunted dopamine response, and needs to take stronger and stronger doses to get the same ‘reward’. These findings lend support to those obese persons who are convinced they have a genetic cause for their problem.