Brain dynamics set your ideal portion size

June 1, 2015

A study published in NeuroImage shows that selection of the ideal portion size relies on specific spatio-temporal brain dynamics. The researchers suggest that those who overeat or “emotional eaters” (whose consumption is triggered by anxiety, sadness, or loneliness) may lack dietary control, but that education could help these groups.

In the research, 21 normal weight women were asked to look at photos of the same dish in varying sizes (from small to large) and select the “ideal” portion size “to stop feeling hungry until an evening meal.” Using neuroimaging, the scientists documented the greater excitement that the women experienced in the visual, salience, and reward regions of the brain when they first saw pictures of portions they subsequently judged to be “too big,” versus the portions that they judged to be “too small” or “ideal.”

The researchers found that activity in different parts of the brain, involved with attention and adaptive behavior, quickly succeeded these reward-related reactions. Brain activity was ultimately highest in the regions involved with attention and adaptive behavior for the portions that the women decided were ideally sized, suggesting that they exercised dietary restraint when making their choices, balancing energetic needs against the desire to control intake.

“We found two mechanisms working in parallel,” said Julie Hudry, Nestlé Research Center. “One involved more in counting—how much food is present, how many calories, and possibly how much reward. The second is this regulatory mechanism—judging what amount is appropriate for me to feel full until the next meal.”

“What we don’t know is if this second mechanism is disrupted somehow in people who tend to overeat,” added Hudry. “Communication around this regulatory mechanism is something that could help people to control their hunger.”