Scientists presenting a new study at a conference this week suggest the reason skipping breakfast makes high calorie food more appealing later in the day is because our brain circuits may be primed toward seeking it when fasting.

Lead author of the study, Tony Goldstone of Imperial College London in the UK, and colleagues, compared people’s MRI brain scans and their eating patterns, both after breakfast and when they skipped it.

They presented their findings at Neuroscience 2012 in New Orleans on Wednesday. Goldstone, who is from Imperial’s MRC Clinical Science Centre, told the press:

“Through both the participants’ MRI results and observations of how much they ate at lunch, we found ample evidence that fasting made people hungrier, and increased the appeal of high-calorie foods and the amount people ate.”

For their study, the team took several functional magnetic resonance images (fMRIs) of 21 normal-weight volunteers who were asked not to have any breakfast when they arrived in the test centre on the mornings of their visits.

After an initial visit, some days the participants ate a large 750-calorie breakfast about one and a half hours before undergoing scans, while on other days they underwent scanning without receiving a breakfast beforehand. They were served lunch after the scans each time, and the scientists observed how much they ate.

On each occasion, participants were also asked to rate the appeal of pictures of high-calorie and low-calorie foods while they underwent brain scanning. They were also asked to rate the appeal of household objects as a control.

The results showed that skipping breakfast increased hunger, appeal of high-calorie foods and food intake at lunch after scanning.

When they compared the brain scans of the breakfast eating and the breakfast skipping visits, the researchers noticed different patterns of activity in the orbitofrontal cortex. This area is situated just above the eyes and influences judgements about pleasantness and reward value of food.

On the days the participants skipped breakfast, this area was more active when they looked at pictures of high-calorie foods than on the day they had breakfast.

The study suggests the orbitofrontal cortex plays a key role in making food choices. The researchers say their findings add weight to previous studies that have suggested fasting is not a good way to lose weight: it appears to “bias” the brain toward seeking out high-calorie foods.

They said it was possible, through looking at the MRI scans, to predict which individuals were “primed” to respond more strongly to high-calorie food.

Funds from the UK Medical Research Council (MRC), the European Union Marie Curie Fellowship, Imperial College Healthcare Charity, and the National Institute for Health Research helped finance the study.

Written by Catharine Paddock PhD