Fatty food: Our brain made us eat it

Researchers already know that the reward centre of the brain values food high in and carbohydrates  more than foods containing only fat or only carbs.

Now a study of 206 adults, published  on June 14 in the journal Cell Metabolism, supports the idea that foods high in both fat and carbohydrates – that is, many processed foods - hijack our body's inborn signals governing food consumption.

The test subjects underwent brain scans while being shown photographs of familiar snacks containing mostly fat, mostly sugar, and a combination of fat and carbs.

Allocated a limited amount of money to bid on their first-choice foods, subjects were willing to pay more for foods that combined fat and carbohydrates.

What's more, the fat-carb combo lit up neural circuits in the reward centre of the brain more than a favourite food, a potentially sweeter or more energy-dense food, or a larger portion size.

Senior author Dana Small, director of Yale University's Modern Diet and Physiology Research Centre, said researchers were surprised to find that  foods containing fats and carbs appear to signal their potential caloric loads to the brain via distinct mechanisms.

“Our participants were very accurate at estimating calories from fat and very poor at estimating calories from carbohydrate.

“Our study shows that when both nutrients are combined, the brain seems to overestimate the energetic value of the food."

Scientists believe our past experience with the nutritive properties of carbohydrates releases dopamine in the brain through an as-yet-unknown metabolic signal.

These kinds of signals seem to help regulate what and how much we eat.

The researchers theorize that the simultaneous activation of fat and carbohydrate signalling pathways launches an effect that human physiology has not evolved to handle.