Why our eyes are bigger than our stomachs

By Helen Albert

Viewing images of high-calorie foods can trigger hunger cravings, suggests research presented at the Endocrinology Society's annual meeting ENDO 2012 in Houston, Texas, USA.

"This stimulation of the brain's reward areas may contribute to overeating and obesity," said lead researcher Kathleen Page (University of Southern California, Los Angeles, USA) in a press statement.

"We thought this was a striking finding, because the current environment is inundated with advertisements showing images of high-calorie foods," she added.

The team used functional magnetic resonance imaging (fMRI) to scan the brain responses of 13 young (15‑25 years), obese Hispanic women when shown images of high-calorie foods, such as cupcakes and nonfood items.

After being shown a selection of similar images, the women were asked to rate their hunger and desire for sweet or savory food on a scale ranging from 1 to 10.

Halfway through the scanning procedure the participants were asked to drink 50 g glucose and during a subsequent scan 50 g fructose to evaluate the effect that this had on hunger ratings and brain activation.

Viewing pictures of high-calorie foods compared with nonfoods triggered blood flow to areas of the brain involved with controlling appetite and satiety; namely, the hypothalamus, striatum, insula, and orbitofrontal cortex. It also increased hunger ratings and desire for sweet and savory foods.

Notably, consuming the sugary drinks significantly increased rather than decreased ratings of hunger and cravings for sweet and savory foods.

"These findings suggest that added sweeteners could be one of the main contributors to the obesity epidemic," said Page.

"We hypothesized that the reward areas in the women's brains would be activated when they were looking at high-calorie foods, and that did happen," she said. "What we didn't expect was that consuming the glucose and fructose would increase their hunger and desire for savory foods.

"Our bodies are made to eat food and store energy, and in prehistoric days, it behooved us to eat a lot of high-calorie foods because we didn't know when the next meal was coming. But now we have much more access to food, and this research indicates added sweeteners might be affecting our desire for it," she concluded.

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