Blood sugar determines how we respond to the sight of food, twin study reveals

The way your brain responds when food appears has more to do with your blood sugar level than with environmental or genetic factors, say researchers from the University of Washington.

Using brain scans of twins, Dr. Ellen Schur and colleagues analyzed how the brain responds to images of high- and low-calorie foods. They wanted to see what changes could be observed when the twins were exposed to these foods, as well as how these changes might affect appetite.

Nutritional needs trump habits or genes

The 21 pairs of identical twins were shown images of non-fattening foods, like fruits and vegetables, and then fattening foods, like pizza and French fries. After these exercises, the participants were offered food from a buffet.

The twin pairs gave similar responses when they were asked to rate their appetite - and they even showed similarities in how much they ate at the buffet. But the brain scans told a different story: Brain activation in the twin with lower blood sugar was greater when the individual was shown images of food.

"Just looking at pictures of high-calorie foods when we are hungry strongly engages parts of the brain that motivate us to eat," said Schur.

So while genetics and upbringing can play a role in weight, the authors concluded, the immediate response to food is driven by the body's nutritional needs.

Source: Society for the Study of Ingestive Behavior

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